  Motivated by a recent observation of good thermoelectric properties in %a
%pyrite material PtSb$_2$, we theoretically study related pyrites %materials in
an attempt to %find a %better thermoelectric material. %Our aim is to seek for
a material which overcomes the suppression of the Seebeck coefficient at high
temperatures.% in PtSb$_2$. We find that PtAs$_2$ and PtP$_2$ are good
candidates, where a larger band gap than in PtSb$_2$ combined with the overall
flatness of the band top gives rise to a monotonically increasing Seebeck
coefficient up to high temperatures. This expectation has been confirmed quite
recently for hole doped PtAs$_2$, where a very large power factor of $\sim$
65$\mu$W/cmK$^2$ at T=440 K is observed.
