(a) The crystal structure of SnTe, in which the green plane depicts one of {110} mirror planes. (b) The face-centered-cubic Brillouin zone, in which the Γ L₁L₂ plane is invariant under reflection about the (110) mirror plane. (c), (d) The band structures of PbTe and SnTe with p orbital projections of cation (red dots) and anion (blue dots). The calculations are performed with optimal lattice constants (6.56 Å for PbTe and 6.40 Å for SnTe). At L, the lowest-lying valence and conduction states associated with even and odd parity eigenvalues are labeled by and , respectively.