  We performed Boltzmann transport calculation to obtain the Seebeck
coefficient, electrical conductivity, electronic thermal conductivity, and
thermoelectric figure of merit (ZT) for Dirac systems. We found an enhancement
of ZT due to the gap opening. When the phonon thermal conductivity is small
enough, the optimum ZT in gapped Dirac system can be larger than 1, which is
preferable for thermoelectric applications.
