The paper discusses the strain-induced phase transition from an antiferromagnetic (AFM) to an alternmagnetic (AM) phase in ReO$_2$. Altern magnets are a new class of collinear compensated magnetic materials that exhibit even (d, g, or i-wave) spin-polarization order in the band structure, setting them apart from conventional ferromagnets and antiferromagnets. The key challenge is to demonstrate controlled transitioning to the AM phase from other conventional phases in a single material. The authors use compressive strain to induce the transition, lifting the Kramer's degeneracy of the band structure in the non-relativistic regime. They show that this transition is accompanied by a metal-insulator transition and calculate the distinct spin-polarized spectral functions of the two phases, which can be detected in angle-resolved photoemission spectroscopy experiments. The study provides the first evidence of strain-tuning conventional AFM states to the new third category of AM magnets, offering potential for applications in data storage, sensors, and spintronics.The paper discusses the strain-induced phase transition from an antiferromagnetic (AFM) to an alternmagnetic (AM) phase in ReO$_2$. Altern magnets are a new class of collinear compensated magnetic materials that exhibit even (d, g, or i-wave) spin-polarization order in the band structure, setting them apart from conventional ferromagnets and antiferromagnets. The key challenge is to demonstrate controlled transitioning to the AM phase from other conventional phases in a single material. The authors use compressive strain to induce the transition, lifting the Kramer's degeneracy of the band structure in the non-relativistic regime. They show that this transition is accompanied by a metal-insulator transition and calculate the distinct spin-polarized spectral functions of the two phases, which can be detected in angle-resolved photoemission spectroscopy experiments. The study provides the first evidence of strain-tuning conventional AFM states to the new third category of AM magnets, offering potential for applications in data storage, sensors, and spintronics.