However, the Portuguese club say that clause is null and void as the playmaker signed a fresh deal in June 2018 after terminating the original one.
"We can confirm that on April 3 the Italian club Sampdoria lodged a claim with FIFA against the Portuguese club Sporting Clube de Portugal related to financial obligations set out in the contract corresponding to the transfer of ... Fernandes," FIFA said in a statement released to British media.
Fernandes was one of a number of players who terminated their contracts at Sporting after a group of some 50 masked men attacked players and staff at the club's training complex in 2018. He later decided to remain with the club.