Mainz have confirmed they're signing permanently Espanyol fullback Aaron Martin.

Marca reports Mainz will pay Espanyol €6m for his transfer.

The Catalan club already received €3m for the 21-year-old left-back in the summer when they sent him on loan to Germany and the total fee could rise to €12m based on variables.

"The progress of Aaron Martin is how we imagined it," Rouven Schroder, the Mainz sporting director, said.

"He is a quality player who immediately stepped up, while he is also young and has potential.

"We hope to see future advances in his development."