TAMPA, Fla. — Slam Corp, the shell company founded by former MLB player Alex Rodriguez, extended its merger deadline with Lynk Global but must refund $81 million to investors who redeemed shares instead of seeking a stake in the direct-to-smartphone satellite operator. The three-month extension gives the shell company until March 25 to complete the transaction, according to a Dec. 26 regulatory filing. After raising $575 million from listing shares on Nasdaq in February 2021 to search for an investment opportunity, Slam’s trust account has dwindled to just $23 million…