The 22-year-old Frenchman, who has spent the last two seasons with the Portuguese side, becomes Steve Coppell´s first signing of the summer.
Royals director of football Nicky Hammond said: "Kalifa is a 6ft 2ins central midfielder who has also played in defence. He has real athletic ability and the technical attributes that should be well suited to the Premiership."
© Copyright PA Sport Ltd 2007, All Rights Reserved.
Do YOU want to write for GiveMeSport? Get started today by signing-up and submitting an article HERE: https://www.givemesport.com/writeforgms