We have conducted magnetotransport measurements on samples of NiFeMnAl and $\mathrm{NiF}{\mathrm{e}}_{1.25}{\mathrm{Mn}}_{0.75}\mathrm{Al}$, both of which are ferromagnetic. The longitudinal resistivity ${\rho }_{xx}$ of both materials exhibits shallow minima at low temperatures because of enhanced electron–electron interaction quantum-interference correction effects. The variation of ${\rho }_{xx}$ with temperature is very weak, with only a 2.5% increase between 10 K and 310 K, consistent with semimetallic behavior. At 310 K, NiFeMnAl exhibits a sharp increase in ${\rho }_{xx}$. No such increase is observed in $\mathrm{NiF}{\mathrm{e}}_{1.25}{\mathrm{Mn}}_{0.75}\mathrm{Al}$. The resistivity upturn in NiFeMnAl coincides with a similarly pronounced change in the ordinary Hall coefficient, which changes sign, indicating two-carrier transport and a shift in the Fermi level, consistent with a temperature-induced Lifshitz transition. The longitudinal magnetoresistance data exhibit excellent agreement with weak-localization theory up to temperatures near room temperature. The temperature-driven sign change in the Hall coefficient is also coincident with a shift in the magnetoresistance from negative to positive, and then oscillations at higher temperature. These dramatic effects indicate multiband transport, which calculations suggest could be caused by the underlying Weyl semimetallic behavior.

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• Electronic structure
• Magnetotransport
• Crystal growth
• Electron microscopy
• Energy-dispersive x-ray spectroscopy
• First-principles calculations
• Hall bar
• Magnetization measurements
• X-ray diffraction