Large magnetothermopower effect in Dirac materials (Sr/Ca)MnBi2

We report temperature and magnetic field dependence of the thermal transport properties in single crystals of (Sr/Ca)MnBi2 with linear energy dispersion. In SrMnBi2 thermopower is positive, indicating hole-type carriers and the magnetic field enhances the thermopower significantly. The maximum change of thermopower is about 1600% in 9 T field and at 10 K. A negative thermopower is observed in CaMnBi2 with dominant electron-type carriers, and, in contrast, the magnetic field suppresses the absolute value of thermopower. First-principle band structure shows that the chemical potential is close to the Dirac-cone-like points in linear bands. The magnetic field suppresses the apparent Hall carrier density of CaMnBi2 below 50 K. The large magnetothermopower effect in (Sr/Ca)MnBi2 is attributed to the magnetic field shift of chemical potential. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3695155]