Recently, evidence has emerged for a field-induced even- to odd-parity superconducting phase transition in $\mathrm{Ce}{\mathrm{Rh}}_2{\mathrm{As}}_2$ [S. Khim et al., Science 373, 1012 (2021)]. Here we argue that the $P4/nmm$ nonsymmorphic crystal structure of $\mathrm{Ce}{\mathrm{Rh}}_2{\mathrm{As}}_2$ plays a key role in enabling this transition by ensuring large spin-orbit interactions near the Brillouin zone boundaries, which naturally leads to the required near-degeneracy of the even- and odd-parity channels. We further comment on the relevance of our theory to FeSe, which crystallizes in the same structure.

• Received 28 June 2021
• Revised 18 November 2021
• Accepted 3 January 2022

DOI:https://doi.org/10.1103/PhysRevB.105.L020505