Gapless nodal lines in a rare-earth-based semimetal

Rare-earth-based semimetals in the ZrSiS family bring into play the potential correlation effects and magnetic ordering from the rare-earth 4f electrons in addition to the topological fermions that this family can support. Here, we investigate the electronic structure of a rare-earth-based ZrSiS-type system using the angle-resolved photoemission spectroscopy technique corroborated by density-functional theory calculations. The experimental results show the presence of multiple gapless Dirac nodes associated with multiple Dirac nodal lines in this system and these observations are well supported by calculated band structures. This work presents an insight into the topology in a rare-earth-based semimetal, which could be important to investigate its interplay with magnetic ordering, correlation effects, and spin-orbit coupling within such ZrSiS-type systems.