  We report giant anisotropy in thermoelectric power factor ($S^2\sigma$) of
marcasite structure-type PtSb$_{1.4}$Sn$_{0.6}$. PtSb$_{1.4}$Sn$_{0.6}$,
synthesized using ambient pressure flux growth method upon mixing Sb and Sn on
the same atomic site, is a new phase different from both PtSb$_2$ and PtSn$_2$
that crystallize in the cubic $Pa\bar{3}$ pyrite and $Fm\bar{3}m$ fluorite unit
cell symmetry, respectively. Giant difference in $S^2\sigma$ for heat flow
applied along different principal directions of the orthorhombic unit cell
mostly stems from anisotropic Seebeck coefficients.
