  We demonstrate that contrary to the common belief the critical temperature Tc
of clean F1/S/F2 spin valves can depend non-monotonically on the angle between
the magnetic moments of the ferromagnetic F1 and F2 layers. Depending on the
system parameters the minimum of Tc may correspond to parallel, antiparallel or
non-collinear mutual orientation of magnetic moments. Such anomalous behavior
can reveal itself only provided the ferromagnetic layers differ from each other
and it completely disappears in the dirty limit.
