We investigated pressure-induced electronic and structural transitions in the quasi-one-dimensional superconducting materials ${\left(\mathrm{Ta}{\mathrm{Se}}_4\right)}_3\mathrm{I}$ using transport measurements and Raman spectroscopy up to 110 GPa. At ambient pressure, ${\left(\mathrm{Ta}{\mathrm{Se}}_4\right)}_3\mathrm{I}$ exhibits a rare coexistence of weak ferromagnetism, charge density wave, and superconducting (SC) states. Applying pressure suppresses the SC-I phase above 3 GPa, while a distinct high-pressure superconducting state (SC-II) emerges at 6.7 GPa with a maximum $T_c$ onset of ∼9.3 K and persisting up to 110 GPa. Raman evidence of structural transition at 5.6 GPa coincides with SC-II emergence, suggesting a direct link between lattice rearrangement and the emergence of SC-II. Our findings establish ${\left(\mathrm{Ta}{\mathrm{Se}}_4\right)}_3\mathrm{I}$ as a unique platform to study the interplay between structure and SC in low-dimensional superconductors.

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• High-pressure studies
• Superconductivity
• 1-dimensional systems
• Ferromagnetic superconductors