Strongly Electron-Correlated Semimetal RuI3 with a Layered Honeycomb Structure

A polymorph of RuI3 synthesized under high pressure was found to have a two-layered honeycomb structure. The resistivity of RuI3 exhibited semimetallic behavior, in contrast to the insulating properties of α-RuCl3. In addition, Pauli paramagnetic behavior was observed in the temperature dependence of the magnetic susceptibility and the nuclear spin–lattice relaxation rate 1/T1. Band structure calculations indicate that the contribution of the I 5p components to the low-energy t2g bands effectively reduces the Coulomb repulsion, leading to semimetallic properties. The physical properties also suggest strong electron correlations in RuI3.