The 21-year-old was part of the Germany outfit which won the under-21 European championships last month and played 27 Bundesliga matches last year.

"The economic dimension, in other words the transfer fee for a player whose contract expires next year, is why we accepted this move," said Schalke sporting director Christian Heidel.

German daily Bild reported that the fee was 37 million euros ($42.3 million).

PSG kick off their Ligue 1 title defence later on Sunday against Caen at the Parc des Princes.

Kehrer will have to fight with Thiago Silva, Presnel Kimpembe and Marquinhos for a place in the French champions' defence.