Schalke announced on Wednesday that they have signed Finnish international forward Teemu Pukki, who scored three goals against them in a recent Europa League play-off tie.
Pukki signed a three-year contract after joining from HJK Helsinki and reportedly cost between one million ($1.4m) and 1.5 million euros, according to German daily Bild.
"In two matches against us, he showed what he was capable of," said Schalke sporting director Horst Heldt.
"We now hope that he'll be a strong addition to our team."
Pukki, 21, scored twice in Helsinki's shock 2-0 defeat of Schalke in the first leg of the Europa League encounter and also claimed a consolation goal in his side's 6-1 loss in the return leg.
He previously spent two seasons with Sevilla, making one appearance for the first team before returning to Finland.