United's first capture of the January transfer window is Billy Paynter.
The striker joins the Blades on loan for the remainder of the season from Championship outfit Doncaster Rovers.
The 29-year-old six-footer arrives on the eve of Saturday's Sky Bet League encounter with Notts County and goes straight into Nigel Clough's plans for the visit to Meadow Lane.
Boss Clough commented: "Billy is a proven striker at this level and he gives us additional options with a busy period of fixtures ahead. He is cup-tied but available for the league games and will be able to share the load with Chris Porter."
Paynter has been with Doncaster since August 2012 and has netted 14 goals in his 28 starts for Doncaster, whilst earlier in his career he scored goals for Port Vale, Hull City, Swindon Town and Leeds, amongst others.