Quenching of Nonrelativistic p-Wave Spin Splitting by c-f Decoupling in CeNiAsO

The extending of spin-space group symmetries to coplanar antiferromagnets has predicted the emergence of odd-parity nonrelativistic spin splittings, making the identification of a practical $p$-wave magnet a central pursuit in spintronics. The layered heavy-fermion oxypnictide CeNiAsO has been widely regarded as the prototypical platform to verify this paradigm, as its commensurate coplanar magnetic configuration is theoretically expected to induce a robust $p$-wave band splitting. Here, we investigate the electronic structure of single-crystal CeNiAsO using ultra-low-temperature, high-resolution, and resonant angle-resolved photoemission spectroscopy (ARPES). Across the consecutive magnetic transitions into the ordered phases, our spectroscopic data reveal neither the expected band folding associated with a spin density wave nor any observable $p$-wave band splitting, demonstrating that the conduction bands retain full Kramers degeneracy. By tracking the temperature dependence of the Ce 4$f$ spectral weight via resonant ARPES, we find no evidence of coherent $c-f$ hybridization near the Fermi level within the magnetically ordered states, confirming that the Ce 4$f$ electrons operate in the localized limit. Our findings establish a clear many-body constraint on projecting real-space magnetic symmetries onto momentum-space electronic bands, demonstrating that geometric symmetry classifications constitute a necessary framework but are not a sufficient condition for nonrelativistic spin splittings in the presence of strong electronic correlations.