Anomalous Thermal Expansion in a CuAl₂-type Superconductor CoZr₂

In this work, we show that the CuAl2-type superconductor CoZr2 and alloyed systems exhibit anomalous thermal expansion in a wide temperature range. We performed neutron powder diffraction X-ray on observed remarkably anisotropic with c-axis negative constant of {\alpha}c < -15 {\mu}K-1 range T = 50-573 K. With decreasing temperature, lattice decreases, while c continuously increases CoZr2. The origin shrinkage/expansion a-axis/c-axis by cooling is explained small change Co-Zr bond systematic decrease Zr-Co-Zr angle. Similar was systems, (Fe,Co,Ni)Zr2 (Fe,Co,Ni,Rh,Ir)Zr2, which suggests phenomenon common feature TrZr2 system. propose zero-thermal metals would be achieved optimizing contrasting a-axis TrZr2.