We have synthesized B20-type Co 1-xFe xGe and Co 1-yNi yGe by a high-pressure method and investigated the band-filling dependence of thermoelectric properties. CoGe shows a large figure of merit (ZT ≈ 0. 11) due to its low resistivity and large negative Seebeck coefficient (S) (- 82 V / K) at 300 K. The sign-crossover of S is observed with increasing Fe concentration. The Boltzmann transport model can explain semi-quantitatively the experimental results, from which we conclude that the large positive or negative S originates from the asymmetric band structure composed of the Dirac cone and the flat band with sharp bends around the Fermi energy.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)