Topological K-theory of the group C*-algebra of a semi-direct product   Z^n rtimes Z/m for a free conjugation action
  We compute the topological K-theory of the group C*-algebra C*_r(G) for a group extension Z^n->G->Z/m provided that the conjugation action of Z/m on Z^n is free outside the origin. 
Martin Langer, Wolfgang Lueck
math.AT math.KT math.OA