China Molybdenum lined up about $700 million of that total as loans from Chinese state-backed banks, including China Construction Bank. BHR raised the remaining amount from obscure entities with names like Design Time Limited, an offshore company controlled by China Construction’s investment bank, according to the Hong Kong filings.

Before the deal was done, BHR also signed an agreement that allowed China Molybdenum to buy BHR’s share of the mine, which the company did two years later, the filings show. That purchase gave China Molybdenum 80 percent ownership of the mine. (Congo’s state mining enterprise kept a stake for itself.)

By the time BHR sold its share in 2019, Mr. Biden controlled 10 percent of the firm through Skaneateles L.L.C., a company based in Washington. While Chinese corporate records show Skaneateles remains a part owner of BHR, Chris Clark, a lawyer for Mr. Biden, said that he “no longer holds any interest, directly or indirectly, in either BHR or Skaneateles.” The Chinese records show that Mr. Biden was no longer on BHR’s board as of April 2020. Mr. Biden did not respond to requests for comment.

A former BHR board member told The New York Times that Mr. Biden and the other American founders were not involved in the mine deal and that the firm earned only a nominal fee from it. The money, the former board member said, went into the firm’s operating funds and was not distributed to its owners.

It is unclear how the firm was chosen by China Molybdenum. Current executives at BHR did not return emails and phone calls seeking comment. “We don’t know Hunter Biden, nor are we aware of his involvement in BHR,” Vincent Zhou, a spokesman for China Molybdenum, said in an email.

A dozen executives from companies involved in the deal, including Freeport-McMoRan and Lundin, said in interviews that they were not given a reason for BHR’s participation. Most of the executives also said they were unaware during the deal of Mr. Biden’s connection to the firm.

Paul Conibear, Lundin’s chief executive at the time, said it was made clear that China Molybdenum was leading the transaction even though the buyer of Lundin’s stake was BHR.