Realization of a three-dimensional (3D) analogue of graphene has been a central challenge in topological materials science. Graphene is stabilized by covalent bonding unlike conventional spin-orbit type 3D Dirac semimetals (DSMs). In this study, we demonstrate the material realization of covalent-type 3D DSMs R8CoX3 stabilized by covalent bonding. We observe that the carrier mobility μ of Dirac fermions reaches 3,000cm2/Vs even in polycrystalline samples, and μ increases with the inverse of the Fermi energy, evidencing significant contributions to charge transport from Dirac electrons. R8CoX3 provides a material platform for exploration of Dirac electrons in three dimensions with wide chemical tunability.
@article{arxiv.2507.06550,
title = {Material realization of spinless, covalent-type Dirac semimetals in three dimensions},
author = {Yuki Tanaka and Rinsuke Yamada and Manabu Sato and Motoaki Hirayama and Max Hirschberger},
journal= {arXiv preprint arXiv:2507.06550},
year = {2025}
}