Thermopower, entropy, and the Mott relation in HgSe:Fe

We have investigated the quantum oscillations in the diffusion thermopower of a HgSe crystal doped with about 1% Fe. The high concentration of Fe has provided sufficient attenuation of phonon-drag quantum oscillations to allow clear observation of oscillations in the diffusion thermopower of a degenerate semiconductor. At high magnetic fields the diffusion oscillations are well represented by the entropy per unit charge, though the measured amplitude is larger than expected by about 50%. At low fields the oscillations shift in phase and agree with those predicted from the electronic relaxation time using the Mott relation.