Zarate, whose move from Qatar´s Al Sadd could be made permanent in the summer, follows the arrivals of David Murphy and James McFadden at St Andrews.
The 20-year-old hit his country´s winner in the final of the Under-20 World Cup last year.
Copyright (c) PA Sport 2008, All Rights Reserved.
Do YOU want to write for GiveMeSport? Get started today by signing-up and submitting an article HERE: http://gms.to/writeforgms