Magnetic Dirac-Kondo semimetal

The interplay among topology, magnetism, and the Kondo effect has the potential to give rise to various exotic quantum phenomena in the heavy-fermion systems, including the emergence of quantum critical points and the formation of topological Kondo insulators. Here, we report the discovery and understanding of a novel heavy-fermion material wherein magnetism, Kondo effect, and topology coexist. We demonstrate that, at high temperatures, due to the existence of the flat bands, the system develops a type A antiferromagnetic (AFM) order. The remaining symmetry of the AFM phase leads to two-fold degenerate Kramer-doublet bands fostering the formation of a non-local Kondo snglet with a notably high Kondo temperature. The onset of the Kondo effect then creates additional single-particle excitation and produces a symmetry-protected Dirac nodal line. Our findings not only illuminate the connections between electronic correlations and topology but also underscore the pivotal role of lattice symmetry in the formation of the Kondo effect.