Uniaxial Negative Thermal Expansion in a Tetragonal V3S-Type Superconductor IrZr3

Recently, uniaxial negative thermal expansion (NTE) has been observed in transition-metal zirconides including tetragonal (CuAl₂-type) CoZr₂ and orthorhombic (Re₃B-type) CoZr₃. Here, we report the observation of uniaxial NTE in tetragonal (V₃S-type) IrZr₃. With increasing temperature, the lattice parameter for the a-axis and volume of IrZr₃ increase, but the lattice parameter for the c-axis decreases. IrZr₃ is a superconductor with a transition temperature of 2.3 K. The present result suggests that uniaxial NTE and related anomalous axis thermal expansion occur in various transition-metal zirconides.