West Ham sign Argentine striker Zarate
The 27-year-old former Lazio and Birmingham forward, who had been playing for Velez Sarsfield in his native Argetina, has signed a three-year-deal with an option for an extra year.
Allardyce had made strengthening his forward line a priority after they struggled for goals last seaosn and flirted with relegation.
Their most high profile striker England international Andy Carroll was injured on several occasions and when he was fit scored just two goals.
"My reaction is that I am very happy to be at West Ham," Zarate said in a statement.
"This is a new chance for me and I want to play.
"I think I played well for Velez this season and that was important for me. I had some good team-mates and they helped to make it a fantastic season for me," added Zarate who has never been capped at senior level but was a member of the Under-20 side that won the 2007 world championship.
Zarate also cited his period at Birmingham as a reason to be positive about his West Ham career.
"I know English football from my time at Birmingham and I hope I will play well and reach the highest possible level."
However, Zarate has attracted nearly as many headlines off the pitch as on the pitch.
In 2010, whilst at Lazio, as well as being suspended for insulting a referee, Zarate was pictured performing a fascist salute whilst in the stands with the club's ultras.
Although his agent claimed the striker was unaware of the significance of his actions, it is not the only time that the Argentine has courted controversy and criticism.
Last year, Zarate was pictured on holiday in the Maldives while he was supposed to be receiving treatment for a skin condition at a time when he was not training with the first team due to a string of disciplinary issues.
Since returning for a second spell at Velez, however, the striker scored 13 goals in 19 appearances, making him the league's top scorer.