Possible inverted band structure in PbPo

Based on empirical evidence, it is suggested that the energy band structure in PbPo may be inverted from that in PbS, PbSe, and PbTe. This inversion would result in PbPo having an L₆⁺ conduction-band edge and an L₆⁻ valence-band edge, implying a negative value of the energy gap $E_G=\left[E\right({L_6}^{-})-E({L_6}^{+}\left)\right]$, and a negative value of $\frac{d{E}_G}{dT}$. We propose an experiment to test this hypothesis.