biostudies-literatureUnknown15(1)Yang XPThe interplay of topology, magnetism, and correlations gives rise to intriguing phases of matter. In this study, through state-of-the-art angle-resolved photoemission spectroscopy, density functional theory, and dynamical mean-field theory calculations, we visualize a fourfold degenerate Dirac nodal line at the boundary of the bulk Brillouin zone in the antiferromagnet YMn<sub>2</sub>Ge<sub>2</sub>. We further demonstrate that this gapless, antiferromagnetic Dirac nodal line is enforced by the combination of magnetism, space-time inversion symmetry, and nonsymmorphic lattice symmetry. The corresponding drumhead surface states traverse the whole surface Brillouin zone. YMn<sub>2</sub>Ge<sub>2</sub> thus serves as a platform to exhibit the interplay of multiple degenerate nodal physics and aNature communications7052https://www.ebi.ac.uk/biostudies/studies/S-EPMC11327286biostudies-literatureA topological Hund nodal line antiferromagnet.PMC11327286Hossain MSGuan SYin JXShi TZheng PBelopolski ICochran TAJiang YXBansil AZhou XXu GLitskevich MYin ZTian ZHasan MZLin CMLi ZChang TRJia SChi SYang XPCheng ZJYao YTZhou HfalseA topological Hund nodal line antiferromagnet.The interplay of topology, magnetism, and correlations gives rise to intriguing phases of matter. In this study, through state-of-the-art angle-resolved photoemission spectroscopy, density functional theory, and dynamical mean-field theory calculations, we visualize a fourfold degenerate Dirac nodal line at the boundary of the bulk Brillouin zone in the antiferromagnet YMn<sub>2</sub>Ge<sub>2</sub>. We further demonstrate that this gapless, antiferromagnetic Dirac nodal line is enforced by the combination of magnetism, space-time inversion symmetry, and nonsymmorphic lattice symmetry. The corresponding drumhead surface states traverse the whole surface Brillouin zone. YMn<sub>2</sub>Ge<sub>2</sub> thus serves as a platform to exhibit the interplay of multiple degenerate nodal physics and a2024-01-01T00:00:00Z2024 Aug2025-04-26T21:21:31.102Z2025-04-06T16:44:55.072ZS-EPMC113272863914774010.1038/s41467-024-51255-3