Spin semimetals are a recently discovered new class of spintronic materials, which exhibit a band gap in one spin channel while exhibiting a semimetallic feature in the other, thus allowing for tunable spin transport. Here, we present experimental verification of spin semimetallic behavior in FeRhCrSi, a quaternary Heusler alloy with saturation moment 2 ${\mu }_B$ and Curie temperature $>400$ K. It crystallizes in the ${\mathrm{L}2}_1$ structure with $50\%$ antisite disorder between Fe and Rh. Below 300 K, it shows a weakly temperature-dependent electrical resistivity with a negative temperature coefficient, indicating normal semimetal or spin semimetal behavior. Anomalous magnetoresistance data reveal the dominant contribution from the asymmetric part, a clear signature of the spin-valve nature, which is retained even at room temperature. The asymmetric part of the magnetoresistance shows an unusual increase with increasing temperature. Hall measurements confirm the anomalous nature of the conductivity originating from the intrinsic Berry curvature, with holes being the majority carriers. Ab initio simulation confirms a unique long-range ferrimagnetic ordering to be the ground state, explaining the origin behind the unexpected low saturation moment. The ferrimagnetic disordered structure confirms the spin semimetallic feature of FeRhCrSi, as observed experimentally.

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• Magnetism
• Spintronics
• Heusler alloy
• Spin valves
• Ab initio calculations
• Density functional theory