The former Spain Under-19 international arrives at the Sixfields Stadium on a free transfer following his release from Hereford in January, and goes straight into the squad for Saturday's game against Macclesfield.
Manager Gary Johnson told the club's official website: "Guillem trained with us on Thursday and I was pleased with what I saw.
"He was on a short-term contract at Hereford earlier this season but he was without a club after leaving them in January.
"We needed to bring in another striker because of the injuries we've got at the moment and Guillem gives us another option.
"He is a player with a good pedigree and I've already seen in training that he is a player with quality."
Source: PA
Source: PA