  The nonadiabatic Heisenberg model presents a nonadiabatic mechanism
generating Cooper pairs in narrow, roughly half-filled "superconducting bands"
of special symmetry. Here we show that this mechanism may be understood as the
outcome of a special spin structure in the reciprocal space, hereinafter
referred to as k-space magnetism. The presented picture permits a vivid
depiction of this new mechanism highlighting the height similarity as well as
the essential difference between the new nonadiabatic and the familiar
Bardeen-Cooper-Schrieffer mechanism.
