A New Three-Dimensional Subsulfide Ir 2 In 8 S with Dirac Semimetal Behavior.

Dirac and Weyl semimetals host exotic quasiparticles with unconventional transport properties, such as high magnetoresistance and carrier mobility. Recent years have witnessed a huge number of newly predicted topological semimetals from existing databases; however, experimental verification often lags behind such predictions. Common reasons are synthetic difficulties or the stability of predicted phases. Here, we report the synthesis of the type-II Dirac semimetal Ir ₂ In ₈ S, an air-stable compound with a new structure type. This material has two Dirac crossings in its electronic structure along the Γ -Z direction of the Brillouin zone. We further show that Ir ₂ In ₈ S has a high electron carrier mobility of ∼10 000 cm ² /(V s) at 1.8 K and a large, nonsaturating transverse magnetoresistance of ∼6000% at 3.34 K in a 14 T applied field. Shubnikov de-Haas oscillations reveal several small Fermi pockets and the possibility of a nontrivial Berry phase. With its facile crystal growth, novel structure type, and striking electronic structure, Ir ₂ In ₈ S introduces a new material system to study topological semimetals and enable advances in the field of topological materials.