above the charge neutral Fermi level (see figure \[fig:fermi\](b)). Thus it is possible that that the observed peak at 200 cm$^{-1}$ is simply indicative of a low energy inter-band transitions and not a signature of Weyl nodes as postulated elsewhere [@chinotti2016electrodynamic].

![Band structure along (001) with Fermi level at 0 meV (blue solid line) and 20 meV above (red dashed line). (b) Calculated optical conductivity for the corresponding Fermi levels.[]{data-label="fig:fermi"}](Fig05a_paqo80_dEf "fig:"){width="45.00000%"}\
![Band structure along (001) with Fermi level at 0 meV (blue solid line) and 20 meV above (red dashed line). (b) Calculated optical conductivity for the corresponding Fermi levels.[]{data-label="fig:fermi"}](S1_fermi.png "fig:"){width="48.00000%"}

To investigate the origin of these two peaks more closely, we decomposed the calculated conductivity into individual inter-band contributions. Figure \[fig:dec\](a) shows the result of that decomposition. These calculations provide more definitive proof to support that the peak in conductivity at 200 cm$^{-1}$ is indeed an inter-band transition from the set of degenerate bands that is mostly above the Fermi level (bands 39, 40) to the immediate higher one (bands 41, 42). This is why when the Fermi level is shifted to higher energies, the occupation in the lower degenerate set of bands (39, 40) and consequently the transition 