Anomalous resistivity upturn in epitaxial L2₁-Co₂MnAl films

Despite of the great scientific and technology interest, highly ordered full-Heusler L2₁-Co₂MnAl films have remained a big challenge in terms of the availability and the electrical transport. Here we report the controllable growth and the intriguing transport behavior of epitaxial L2₁-Co₂MnAl films, which exhibit a low-temperature (T) resistivity upturn with a pronounced T^1/2 dependence, a robust independence of magnetic fields, and a close relevance to structural disorder. The resistivity upturn turns out to be qualitatively contradictory to weak localization, particle-particle channel electron-electron interaction (EEI), and orbital two-channel Kondo effect, leaving a three-dimensional particle-hole channel EEI the most likely physical source. Our result highlights a considerable tunability of the structural and electronic disorder of magnetic films by varying growth temperature, affording unprecedented insights into the origin of the resistivity upturn.