  We report the controllable growth and the intriguing transport behavior of
high-spin-polarization epitaxial L21-Co2MnAl films, which exhibit a
low-temperature (T) resistivity upturn with pronounced T1/2 dependence, close
relevance to structural disorder, and robust independence of magnetic fields.
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
spin polarization and the resistivity upturn.
