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?