  The interpretation of some recent measurements of spin-dependent voltage for
which the electric conduction does not play a role rises some new fundamental
questions about the effects of spin-dependent heat currents. A two spin-channel
model is proposed in order to describe the effect of out-of-equilibrium
spin-dependent heat carriers in electric conductors and insulators. It is shown
that thermal spin-accumulation can be generated by the heat currents only over
an arbitrarily long distance for both electric conductors or electric
insulators. The diffusion equations for thermal spin-accumulation are derived
in both cases, and the principle of its detection based on Spin-Nernst effect
is described.
