New experimental arguments for two-channel Kondo physics due to As vacancies in the layered compound ZrAs_1.58Se_0.39

The scattering of conduction electrons off structural two-level systems (TLS) can lead to a non-magnetic two-channel Kondo (2CK) effect, but experimental evidence is rare. In our previous works, we have shown that the remarkable differences in the magnetic-field-independent -|A|T1/2 term in the low-temperature electrical resistivity ρ(T) of the layered compound ZrAs1.58Se0.39 are consistent with 2CK physics based on structural TLS. Here, we present a systematic study of the a axis resistivity of various Zr(As,Se)2 single crystals and an effect of thermal annealing on previously measured ZrAs1.58Se0.39 samples. We confirm the absence of enhanced variations in the anisotropy of ρ(T) and point to annealing-induced changes in the -|A|T1/2 term, providing further evidence for the 2CK effect due to As vacancies in ZrAs1.58Se0.39 © 2025 Author(s).