We report a metal-insulator transition (MIT) in the half-filled multiorbital antiferromagnet (AFM) ${\mathrm{BaMn}}_2{\mathrm{Bi}}_2$ that is tunable by a magnetic field perpendicular to the AFM sublattices. Instead of an Anderson-Mott mechanism usually expected in strongly correlated systems, we find by scaling analyses that the MIT is driven by an Anderson localization. Electrical and thermoelectrical transport measurements in combination with electronic band calculations reveal a strong orbital-dependent correlation effect, where both weakly and strongly correlated $3d$-derived bands coexist with decoupled charge excitations. Weakly correlated holelike carriers in the $d_{xy}$-derived band dominate the transport properties and exhibit the Anderson localization, whereas other $3d$ bands show clear Mott-like behaviors with their spins ordered into AFM sublattices. The tuning role played by the perpendicular magnetic field supports a strong spin-spin coupling between itinerant holelike carriers and the AFM fluctuations, which is in sharp contrast to their weak charge coupling.

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• Anderson localization
• Electrical conductivity
• Electronic structure
• Metal-insulator transition
• Transport phenomena
• Strongly correlated systems