${\mathrm{Co}}_2\mathrm{MnGa}$ is a ferromagnetic Weyl semimetal that may exhibit a giant anomalous Hall effect and negative longitudinal magnetoresistance (LMR), both of which originate from its band structure, giving rise to a large Berry curvature and a chiral anomaly. A previous positron annihilation study revealed that even in a highly ordered, stoichiometric bulk single crystal of ${\mathrm{Co}}_2\mathrm{MnGa}$, a large number of single vacancies are inevitably present. In the present work, density measurements indicated that the vacancy concentration could reach up to $\sim 1$ at. %, but a giant anomalous Hall conductivity (AHC) of $\gtrsim 1500$ S/cm was observed. Further analysis showed that the giant AHC is maintained by an intrinsic contribution of $\sim 1000$ S/cm, which is lower than the theoretical value for a perfect crystal (1500–2000 S/cm), along with an additional extrinsic contribution of $\sim 500$ S/cm, mainly caused by skew scattering. The ab initio calculation suggested that the electronic states along the Weyl nodal lines are not significantly altered, provided that only Ga vacancies are introduced. However, the Fermi level is shifted below the Weyl nodes, which decreases the intrinsic AHC. Negative LMR and its ${\cos }^2\theta$-like angular dependence were also observed. However, the major part of the LMR originates from the dynamics of magnetic domains under an applied magnetic field, whereas the chiral anomaly, if present, appears to have only a limited effect in the present condition.

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• Electrical properties
• Electronic structure
• Magnetism
• Spintronics
• Alloys
• Ferromagnets
• Half-metals
• Semimetals
• Weyl semimetal
• Band structure methods
• Positron annihilation spectroscopy
• Transport techniques