Crystallographic disorder and electron scattering on structural   two-level systems in ZrAs1.4Se0.5
  Single crystals of ZrAs1.4Se0.5 (PbFCl type structure) were grown by chemical vapour transport. While their thermodynamic and transport properties are typical for ordinary metals, the electrical resistivity exhibits a shallow minimum at low temperatures. Application of strong magnetic fields does not influence this anomaly. The minimum of the resistivity in ZrAs1.4Se0.5 apparently originates from interaction between the conduction electrons and structural two-level systems. Significant disorder in the As-Se substructure is inferred from X-ray diffraction and electron microprobe studies. 
M. Schmidt, T. Cichorek, R. Niewa, A. Schlechte, Y. Prots, F. Steglich   and R. Kniep