The Role of Lattice Symmetry and Band Topology in Correlation Effects

We explore the critical role of lattice symmetry, quantum geometry and band topology in the development of Kondo effect and magnetism, in a topological heavy-fermion material CeCo₂P₂. At high temperatures, we show the itinerant Co c-electrons form non-atomic bands with a narrow bandwidth, driving a high antiferromagnetic transition temperature. The quantum geometry of these bands favors in-plane ferromagnetism, while their weak dispersion along the z-axis leads to out-of-plane antiferromagnetic. At lower temperatures, we uncover a novel phase where Co-antiferromagnetism coexists with the Kondo effect. This phase is linked to PT-protected Kramers doublets and the filling-enforced metallic nature of the c-electrons in the antiferromagnetic phase. The onset of the Kondo effect, in conjunction with glide-mirror-z-symmetry, generates nodal-line excitations near the Fermi level. Our findings emphasize the critical role of lattice symmetry, quantum geometry, and the interplay between Kondo physics and magnetism in the correlation-driven behavior of CeCo2P2.