Electronic Band Topology in the Orthorhombically Distorted Nodal Line Semimetal Candidate CeAsS

Rare-earth–based materials derived from the ZrSiS family have emerged as ideal platforms to explore the interplay between magnetism, 4f-electron correlations, topological band structures and crystalline symmetry. Extending this landscape, we investigated the closely related compound CeAsS, which crystallizes in an orthorhombic Pnma structure through a combination of angle-resolved photoemission spectroscopy , Density functional theory  calculations, and comprehensive thermodynamic and transport measurements. Magnetic susceptibility, magnetization, and specific heat reveal a long-range antiferromagnetic transition at T_N = 9.5 K, which shifts to lower temperature under applied field, and a field-induced phase emerging above 6 T. Electrical resistivity confirms metallic behavior, while magnetotransport measurements uncover a large, non-saturating magnetoresistance exceeding 600% at 1 K and 13 T, accompanied by Shubnikov–de Haas oscillations. ARPES spectra collected in the paramagnetic phase display a diamond-shaped Fermi surface with distinct corner pockets and linearly dispersive surface bands forming gapless Dirac-like crossings around 150 meV below fermi level. These findings identify CeAsS as a correlated semimetal where antiferromagnetism, 4f-electron interactions, and Dirac-like dispersions coexist, providing a promising platform to study the coupling between magnetic order and topological electronic states in lanthanide pnictide-chalcogenides.