  We study the problem of thermoelectricity and propose a simple microscopic
mechanism for the increase of thermoelectric efficiency. We consider the cross
transport of particles and energy in open classical ergodic billiards. We show
that, in the linear response regime, where we find exact expressions for all
transport coefficients, the thermoelectric efficiency of ideal ergodic gases
can approach Carnot efficiency for sufficiently complex charge carrier
molecules. Our results are clearly demonstrated with a simple numerical
simulation of a Lorentz gas of particles with internal rotational degrees of
freedom.
