Barcelona B have signed Santiago Ramos Mingo on a free transfer from Boca Juniors.
The 18-year-old signed a 3-year deal with Barcelona, which includes a $66 million buyout clause.
The deal has sparked controversy within the Argentine club, with team president Jorge Amor Ameal hitting out at Barcelona's practices.
"Legally we are in a position to state that the player is ours. There is a clause in FIFA ensuring that the player belongs to us because of his income. Our lawyers are working and we will fight it."