  Coherence peak effects in a superconductor induced by a thermal spin current
are reported. We measured inverse spin Hall effects induced by spin injection
from a ferrimagnetic insulator Y$_3$Fe$_5$O$_{12}$ into a superconductor NbN
using longitudinal spin Seebeck effects. In the vicinity of the superconducting
transition temperature of the NbN, a large enhancement of the spin Seebeck
voltage is observed, whose sign is opposite to that for the vortex Nernst
effect, but is consistent with a calculation for a coherence peak effect in the
superconductor NbN.
