help finding info about officer

around half a year ago i read the book Berlin: The Downfall 1945 by Antony Beevor, from what I remember it mentioned a "famous" Russian officer who fought for the germans with equal minded (other traitors) against the russians, this unit participated in the fight for berlin and the battles immidiatly around the city I hope somebody can help me finding the name and some info about this officer and the unit he was commanding

the only thing I have been able to find so fare was, Andrey Vlasov, but from what i remember its not him I am thinking of, and from what I could find he didn't take part in the Battle of berlin

I realy hope you can help me out !!!