United boss Nigel Clough has added midfielder Kieran Wallace to his squad until the end of the season.
The former England U17 international, who came through the ranks at Nottingham Forest, where he played in a FA Youth Cup semi-final, joins on a free transfer having been on non-contract terms at Ilkeston FC following his release from the City Ground.
Wallace has featured for United's U21s as a trialist in recent weeks, the most recent performance coming in Tuesday's draw with Bradford City at Shirecliffe.
He joins former Ilkeston team-mate Che Adams, who signed for the Blades earlier this month.
Meanwhile, CJ Hamilton, who is part of the Blades development squad has joined Mickleover Sports FC on a youth loan to gain some first-team experience.