Baker McKenzie is facing a hefty malpractice suit over its work on behalf of a Spanish client who used the firm in a failed effort to recover ownership of a Siberian coal mine that the client says is valued at over $200 million.

In a suit filed last month in state court in Chicago, where the global law firm was founded, Daniel Rodriguez and his British company Lehram Capital Investments Ltd. allege that attorneys for the firm failed to detail connections in Russia that might have affected their advice on his claims.