Dutch club AZ Alkmaar have demanded a payment of €7.5 million from Middlesbrough striker Afonso Alves after claiming he broke an agreement to join the club from Heerenveen earlier this year.

AZ say Alves had agreed in principle to join them during the transfer window, but the Alkmaar club failed to reach a deal with Heerenveen by December 31st and the player instead decided to join Boro.

The case between AZ and Alves has gone to arbitration and the club's lawyer, Eric Vile, said: "We are claiming this amount of money on the basis of Fifa's rules."

The hearing will continue next month.