Indicate
by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.
Form 20-F [ ] Form 40-F [X]
Pursuant
to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the
undersigned, thereunto duly authorized.

SIGMA
LITHIUM FILING LEGAL APPEAL AGAINST UNWARRANTED DECISION BY A LOCAL JUDGE;
“FAKE NEWS” CAMPAIGN
COINCIDES WITH RECORD EARNINGS
São Paulo, May 18,
2026 – Sigma Lithium Corporation (NASDAQ: SGML, TSX-V:SGML BVMF: S2GM34) (“Sigma Lithium” or the “Company”),
the largest producer of lithium oxide concentrate in the Americas¹ and dedicated to industrializing socially and environmentally
sustainable lithium materials to supply global producers of batteries for energy security, announces that the Company is filing a legal
appeal against a decision issued on Sunday, May 17, by a local judge from a local court in Aracuai, Vale do Jequitinhonha.
The local decision
included the potential for a legal collateral of US$10 million for the local court. The Company emphasizes this amount would be due only
in the event the charges result in a final negative ruling, after the full due legal process is completed in Brazil, including the
rights to appeal in the appropriate state and federal courts, including the Supreme Tribunal of Justice (STJ) and Supreme Court of Brazil.
The other elements
in the ruling are also not expected to be enforced until the completion of due legal process. Legal jurisprudence for similar cases indicates
a timeline of multiple years until this happens. As such, no payments are due or required.
Sigma Lithium believes the decision
is unwarranted and in dissonance with Brazil’s strong rule of law: due process was not followed.
A significant amount of legal
evidence was filed by the Company with the court.
The surprising ruling followed a
visit by legal authorities to Sigma Lithium’s operations, where the Company’s conformity with all Brazilian environmental
rules was verified, including:
| · | Absence
of tailing dams and 100% dry stacking of tailings. |
| · | 100%
reuse of water by the Greentech Processing Plant, for which the verification included a visit to the Company’s inbound sewage treatment
plant that removes fecal residues from the water utilized. |
| · | Bio-regeneration
of the Company’s rock piles, visually evidenced by growing vegetation. |
| · | Low
levels of noise (even at the mine pit). |
| · | Low
levels of dust, resulting from water trucks running full time at the mining operations conducting site wetting of mining pits and piles. |
PUBLIC HEARING
The visit by the legal authorities
occurred on the same day of a public hearing held for the local community, where more than 200 people from Sigma Lithium’s neighboring
communities attended to demonstrate their support for the approximately 19,000 jobs generated by the Company in the region, ushering in
significant shared prosperity in Vale do Jequitinhonha.
The overwhelming community support
for Sigma Lithium had already been demonstrated in a previous public hearing for the issuance of the Company’s environmental license,
when over 2,000 people attended and 91% of the depositions heard were favorable to Sigma Lithium’s operations and expansion plans.
ANOTHER “FAKE
NEWS” CAMPAIGN COINCIDES WITH RECORD EARNINGS
Prior even to the official
issuance of the legal decision yet another negative online “fake news” media campaign was launched against the
Company, disseminating false, inaccurate, and misleading information, including videos and photos from the operations of other companies
claiming to show Sigma Lithium’s operations.
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More importantly, the campaign
was launched on a Sunday prior to the official issuance of the legal decision and just after Sigma Lithium posted record earnings on Friday
(for 1Q26).
The timing of this negative “fake
news” media campaign against the Company, just after a positive announcement or event and leading to substantial stock volatility
(the share price fell by 15% today), fits a pattern first reported by the Company on January 23rd, 2026. Sigma Lithium remains in close
contact with the appropriate authorities regarding the issue, including FINRA (US Securities and Exchange Commission).
ABOUT SIGMA LITHIUM
Sigma Lithium Corporation (NASDAQ:
SGML, TSXV: SGML, BVMF: S2GM34), (“Sigma Lithium” or “the Company”) is the largest producer of lithium oxide concentrate
in the Americas¹ and dedicated to industrializing socially and environmentally sustainable lithium materials to supply global producers
of batteries for energy security.
The Company runs one of the
world’s largest lithium production sites—the fifth-largest industrial-mineral complex for lithium oxide concentrate—at
its Grota do Cirilo operation in Brazil. Sigma Lithium is at the forefront of environmental and social sustainability in the electric
battery materials supply chain. The Company’s Greentech Industrial Plant combines the reuse of 100% of water, zero use of toxic
chemicals, zero tailings and the use of 100% renewable electricity. For more than two years Sigma Lithium has not experienced an accident
with lost time.
Sigma Lithium currently has
a nameplate capacity to produce 270,000 tonnes of lithium oxide concentrate on an annualized basis (approximately 38,000–40,000
tonnes of LCE) at its mine and state-of-the-art Greentech Industrial Plant. The Company has initiated a Phase 2 expansion designed to
close to double production capacity to 520,000 tonnes. For more information about Sigma Lithium, visit our website
FOR ADDITIONAL INFORMATION PLEASE
CONTACT
Anna Hartley,
Vice President of Global Banking and Investor Relations
anna.hartley@sigmalithium.com.br
+44 7866 458 093
Mariana Bengtson,
Investor Relations Manager
mariana.bengtson@sigmalithium.com.br
+55 11 9 2144 2750
Sigma
Lithium
 |
Sigma Lithium |
 |
@sigmalithium |
 |
@SigmaLithium |
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FORWARD-LOOKING
STATEMENTS
This
news release includes certain “forward-looking information” under applicable Canadian and U.S. securities legislation, including
but not limited to statements relating to timing and costs related to the general business and operational outlook of the Company, the
environmental footprint of tailings and positive ecosystem impact relating thereto, donation and upcycling of tailings, timing and quantities
relating to tailings and Green Lithium, achievements and projections relating to the Zero Tailings strategy, achievement of ramp-up volumes,
production estimates and the operational status of the Grota do Cirilo Project, and other forward-looking information. All statements
that address future plans, activities, events, estimates, expectations, or developments that the Company believes, expects, or anticipates
will or may occur is forward-looking information, including statements regarding the potential development of mineral resources and mineral
reserves which may or may not occur. Forward-looking information contained herein is based on certain assumptions regarding, among other
things: general economic and political conditions; the stable and supportive legislative, regulatory and community environment in Brazil;
demand for lithium, including that such demand is supported by growth in the electric vehicle market; the Company’s market position
and future financial and operating performance; the Company’s estimates of mineral resources and mineral reserves, including whether
mineral resources will ever be developed into mineral reserves; and the Company’s ability to operate its mineral projects including
that the Company will not experience any materials or equipment shortages, any labor or service provider outages or delays or any technical
issues. Although management believes that the assumptions and expectations reflected in the forward-looking information are reasonable,
there can be no assurance that these assumptions and expectations will prove to be correct. Forward-looking information inherently involves
and is subject to risks and uncertainties, including but not limited to that the market prices for lithium may not remain at current
levels; and the market for electric vehicles and other large format batteries currently has limited market share and no assurances can
be given for the rate at which this market will develop, if at all, which could affect the success of the Company and its ability to
develop lithium operations. There can be no assurance that such statements will prove to be accurate, as actual results and future events
could differ materially from those anticipated in such statements. Accordingly, readers should not place undue reliance on forward-looking
information. The Company disclaims any intention or obligation to update or revise any forward-looking information, whether because of
new information, future events or otherwise, except as required by law. For more information on the risks, uncertainties and assumptions
that could cause our actual results to differ from current expectations, please refer to the current annual information form of the Company
and other public filings available under the Company’s profile at www.sedarplus.com.
Neither the TSX Venture Exchange
nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for
the adequacy or accuracy of this news release.
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