Anomalous semiconductorlike transport induced by the Curie transition in a $\mathrm{C}{\mathrm{o}}_{51}{\mathrm{V}}_{31}\mathrm{G}{\mathrm{a}}_{18}$ metamagnetic Heusler alloy is evidenced through a combination of experimental and theoretical investigations. The studied alloy crystallizes in $L{2}_1$ cubic austenite at room temperature and transforms into $D{0}_{22}$ tetragonal martensite during cooling, accompanied by an abrupt change of magnetization. Under ambient pressure, a distinct negative temperature coefficient of resistance is observed within the Curie transition region. With increasing hydrostatic pressure, this anomaly is progressively suppressed and eventually vanishes when the martensitic transformation occurs above the Curie temperature ($T_{\mathrm{C}}$). Combined with Hall resistivity measurements, fitting the anomalous segment of the resistivity data reveals an extremely small activation energy ($\mathrm{\Delta }{E}_{\mathrm{g}}$) of $\sim 11.98\pm (0.135$) meV, suggesting a thermal activation process close to $T_{\mathrm{C}}$. Moreover, first-principles calculations identify a narrow band gap in the minority spin channel at the high-symmetry $X$ point, formed between the conduction and valence bands with contributions from V-$e_{\mathrm{g}}$ and Co-$t_{2\mathrm{g}}$ orbitals, respectively, near the Fermi level ($E_{\mathrm{F}}$). The observation of a purely positive linear magnetoresistance, occurring exclusively within the temperature range from $T_{\mathrm{C}}$ to 190 K, further corroborates this unique electronic band structure. This confirms that the Curie transition directly induces the formation of a narrow band gap, which in turn gives rise to the observed anomalous semiconductorlike transport in the studied alloy.

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• Magnetoresistance
• Pressure effects
• Heusler alloy
• First-principles calculations
• Resistivity measurements