  Thermoelectric devices are heat engines, which operate as generators or
refrigerators using the conduction electrons as a working fluid. The
thermoelectric heat-to-work conversion efficiency has always been typically
quite low, but much effort continues to be devoted to the design of new
materials boasting improved transport properties that would make them of the
electron crystal-phonon glass type of systems. On the other hand, there are
comparatively few studies where a proper thermodynamic treatment of the
electronic working fluid is proposed. The present article aims to contribute to
bridge this gap by addressing both the thermodynamic and transport properties
of the thermoelectric working fluid covering a variety of models, including
interacting systems.
