different inter-band contribution indicates that in this structure the peak is primarily from transitions between the previously degenerate bands, i.e., bands 37$\rightarrow$38 and 39$\rightarrow$40 (Band labels given in Fig. \[fig:bs\]). Although there is not much evidence from our experiment to choose one over the other, we do not favor this as the correct interpretation of our data as a canted order is not supported by neutron scattering experiments or theoretical considerations. However, this calculation further elucidates the fact that this peak is not a signature of Weyl node, even in a band structure that incorporates the effects of canted AFM order.

A possible explanation for the discrepancy in amplitude of the 200 cm$^{-1}$ peak would be electronic correlation effects which can potentially add to the intra-band conductivity but would not be captured through simple subtraction of the Drude contribution. As an alternative to this peak being an inter-band excitation, it may arise from the coupling of conduction electrons to magnetism. Neutron scattering experiments on YbMnBi$_2$ [@FuhrmanPrivateCommunication] show prominent spin wave excitations in the energy range $\sim$ 120 - 340 cm$^{-1}$ which matches the energy scale of the low energy peak observed in conductivity. The extent of this coupling is hard 