An experimental test of the thermopower equation

Experimental thermopower data are almost always interpreted in terms of the well-known thermopower equation which relates the diffusion thermopower to the energy derivative of the conductivity,S=LeT (∂ln σ/∂∊)μ, or an equivalent result. The unknown details of the energy dependence of the scattering in the conductivity have precluded definitive testing of this result. The application of a magnetic field introduces a few complexities, but makes a definitive test of the thermopower equation possible in principle due to the scattering-independence of the high-field Hall conductivity of each band. This paper presents high-field Nernst-Ettinghausen data for Cd and W which were taken with this in mind. The results are not in good agreement with theory, which may have serious repercussions for the theory of thermopower.