$\alpha \text{-MnTe}$ is a $p$-type semiconducting altermagnet with a Néel temperature near $300\text{K}$. Due to the altermagnetic nature, $\mathcal{PT}$ symmetry is broken and Kramers degeneracy is lifted in the valence band maxima along the $\mathrm{\Gamma }\text{−}K$ line and the $A$ point. However, the energy difference is found to be small, and any small shift in the spectrum can dramatically change the linear-response transport properties. Here we show that a strain modulating the [0001] axis of the unit cell by $\sim \pm 0.5\%$ can significantly change the transport signature by switching the thermal window between the two regions of the valence band. When the $\mathrm{\Gamma }\text{−}K$ line is dominating, the planar Hall effect and the anisotropic magnetoresistance can be enhanced by an order of magnitude, with the maximum up to $\sim 70\%$.

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• Altermagnetism
• Antiferromagnetism
• Magnetoresistance
• Spin-orbit coupling
• Boltzmann theory
• Density functional calculations
• Strain engineering