The value of Soros Fund Management’s publicly disclosed holdings dropped by 37 percent to $3.5 billion as of the end of the last quarter, according to a government filing Monday. Soros acquired 1.7 percent of Barrick, making it the firm’s biggest U.S.-listed holding. Soros also disclosed owning call options on 1.05 million shares in the SPDR Gold Trust, an exchange-traded fund that tracks the price of gold.