Honeycomb‐Structure RuI₃, A New Quantum Material Related to α‐RuCl₃

Abstract The layered honeycomb lattice material α‐RuCl₃ has emerged as a prime candidate for displaying the Kitaev quantum spin liquid state, and as such has attracted much research interest. Here a new layered honeycomb lattice polymorph of RuI₃, a material that is strongly chemically and structurally related to α‐RuCl₃ is described_. The material is synthesized at moderately elevated pressures and is stable under ambient conditions. Preliminary characterization reveals that it is a metallic conductor, with the absence of long‐range magnetic order down to 0.35 K and an unusually large T‐linear contribution to the heat capacity. It is proposed that this phase, with a layered honeycomb lattice and strong spin–orbit coupling, provides a new route for the characterization of quantum materials.