Siklos spacetimes as homogeneous Ricci solitons

We consider a well-known class of homogeneous solutions of the Einstein–Maxwell equations found by Siklos and prove that all these spacetimes are nontrivial Ricci solitons. In particular, these examples show that several rigidity results for homogeneous Lorentzian gradient Ricci solitons do not extend to the non-gradient case. (paper)