Soros Fund Management, the investment vehicle of hedge fund billionaire George Soros, appears to have added exposure to some crypto companies before the end of last year, although the nature of the trades is not clear.

According to a 13F filing with the U.S. Securities and Exchange Commission (SEC) dated Dec. 31, Soros Fund Management purchased 39.6 million worth convertible debentures of crypto miner Marathon Digital Holdings (MARA). Convertible debentures are types of long-term debt issued by a company that can be converted into stock after a specified period of time.

The fund was also showing ownership of call options and put options on 50,000 shares of MicroStrategy (MSTR). Soros' 13F from three months earlier disclosed only put options on 50,000 shares. In addition to those common stock bets/hedges, the fund continued to hold nearly $200 million in MicroStrategy preferred shares. MicroStrategy could be considered a proxy for holding bitcoin because of the company's large crypto holdings.

A put option gives the buyer the right but not the obligation to sell while a call option gives the buyer the right but not the obligation to buy.

The bet is likely a hedging strategy on MicroStrategy shares through option play, a trader told CoinDesk.

The fund also disclosed a short position on beleaguered crypto-focused bank Silvergate Bank (SI), holding 100,000 shares worth of put options. The filing being as of the end of 2022, it's unclear now whether Soros Management remains short Silvergate.

The Soros Fund has previously been reported to own bitcoin, during the bull run of 2021.

Read more: Ken Griffin's Citadel Securities Discloses 5.5% Stake in Crypto Bank Silvergate