Two-Channel Kondo Physics due to As Vacancies in the Layered Compound ZrAs1.58Se0.39

We address the origin of the magnetic-field-independent -vertical bar A vertical bar T-1/2 term observed in the low-temperature resistivity of several As-based metallic systems of the PbFCl structure type. For the layered compound ZrAs1.58Se0.39, we show that vacancies in the square nets of As give rise to the low-temperature transport anomaly over a wide temperature regime of almost two decades in temperature. This low-temperature behavior is in line with the nonmagnetic version of the two-channelKondo effect, whose origin we ascribe to a dynamic Jahn-Teller effect operating at the vacancy-carrying As layer with a C-4 symmetry. The pair-breaking nature of the dynamical defects in the square nets of As explains the lowsuperconducting transition temperature T-c approximate to 0.14 K of ZrAs1.58Se0.39 compared to the free-of-vacancies homologue ZrP1.54S0.46 (T-c approximate to 3.7 K). Our findings should be relevant to a wide class of metals with disordered pnictogen layers.