At what energy is Seebeck coefficient calculated?

[dyelb7]

Seebeck coefficient changes with energy and temperature. I recently thought that when Seebeck coefficients are reported, the energy corresponds to Fermi energy and temperature to room temperature, but this paper got me thinking.

Fig.4 tells us that the Seebeck coefficient at Fermi level is positive. However, Mg2Si is an n-type semiconductor with negative Seebeck coefficient (as Fig.5 confirms). I always thought Seebeck coefficient is calculated at Fermi level, but the two figures suggest otherwise. Would someone please explain where I am mistaken?

 

[BigJDubs]

The Seebeck coefficient can indeed change with energy and temperature. It is typically reported at the Fermi level and room temperature, but this is not always the case. For example, in Fig.4 of the paper you referenced, the Seebeck coefficient is reported at a temperature of 500K. As for the discrepancy between Fig.4 and Fig.5, it is likely due to differences in the doping concentrations of the samples used in the measurements. In the case of Fig.4, the sample was heavily doped with Mg, which produces a higher Seebeck coefficient than a sample with a lighter doping concentration.