West Ham have signed Tomas Soucek on loan until the end of the season with an option to buy.
The Czech Republic international joins from Slavia Prague and the Hammers have the option to make the deal permanent in the summer.
Struggling West Ham have paid 4.5 million euros (£3.8m) now, with a further 20.7m euros (£17.5m) due to sign him permanently if they stay up, the PA news agency understands.
Soucek, 24, has 20 senior caps and becomes the second addition to David Moyes’ squad at the London Stadium following the return of goalkeeper Darren Randolph.
“We are delighted to welcome Tomas to West Ham United,” Moyes told the official website.
“I think that he gives us a lot of different qualities, but most importantly he fits the profile of the player we want to bring to the club.
“He is young and hungry but with an established pedigree and proven talent.”
Despite being a defensive midfield player, Soucek has hit 31 goals in 111 league appearances for Slavia, where he was also the club captain.
Links between Soucek and West Ham arose earlier this week, as Moyes looked for extra quality in midfield.
The Hammers are currently lingering one place above the relegation zone, and face league leaders Liverpool on Wednesday night.