Hammers boss Alan Pardew had earlier seen a deal for Barcelona’s Gabri fall through before deciding to take the plunge for the Argentine international.
Lionel, 27, was Deportivo’s club captain having spent 8 years at the Estadio Riazor making more than 250 appearances for the Spanish side; however, he has found first team opportunities limited this year under current boss Joaquin Caparros.
He can play in both defence and midfield and will be looking to impress upon his move to the East End in order to try and cement a place in the Argentine World Cup squad for the finals in Germany.