UPDATE 1-Nuclear startup Oklo to go public in US via Sam Altman's SPAC

(Adds details of deal throughout, context on SPAC market in paragraph 5)

July 11 (Reuters) - Sam Altman-backed Oklo has agreed to go public in the United States through a merger with his blank check firm in a deal that values the nuclear startup at $850 million, the companies said on Tuesday.

Altman is bringing together Oklo that provides emission-free and affordable energy solutions and his special purpose acquisition company, AltC Acquisition Corp, in a deal that will fetch the combined company up to $500 million.

Altman, CEO of OpenAI - the AI startup behind the viral chatbot ChatGPT - co-founded AltC Acquisition Corp, with Churchill Capital in July 2021, and has served as its CEO and chairman of Oklo.

The deal comes as climate awareness and investor interest in sustainable business practices have surged with money managers looking to factor in environmental social governance (ESG) policies.

Still, the SPAC market has been on a downward spiral since last year after gaining popularity in 2020. The sector has taken a hit amid higher investor redemptions and tightening regulatory scrutiny.

The companies expect the deal to close in late 2023 or early 2024, following which the combined entity will trade on the New York Stock Exchange under the ticker "OKLO."

SPACs are companies that are listed on exchanges but have no business operations. They use the pool of capital raised through an initial public offering to merge with a privately held company, in a deal that then takes it public.

(Reporting by Manya Saini in Bengaluru; Editing by Shinjini Ganguli)