We investigate the low-energy electronic properties and construct the effective
model Hamiltonians in the normal state for new materials BaPtSb and BaPtAs with ordered
honeycomb structures. The preliminary experimental study suggested that the former
compound may be a candidate of the time-reversal symmetry breaking superconductors. The
low-energy electronic structures obtained from the first principles calculation mainly consist
of Pt 5d and Sb/As 5p/4p orbitals, where there exist the strong hybridizations between both
orbitals. We show that the main parts in the low-energy region including the Fermi surface
are well described using renormalized 3 bands consisting of dominant Pt 2 bands and Sb/As 1
band. Our result provides a starting point for microscopic investigation in the superconducting
states for the materials with the hexagonal structure.
