We report pressure-driven evolution of the superconducting transition temperature ($T_{\mathrm{c}}$) and upper critical field $B_{\mathrm{c}2}$ $\left(0\right)$ of strong-coupling superconductor ${\mathrm{Ti}}_4{\mathrm{Ir}}_2\mathrm{O}$ that possesses an unusually large $B_{\mathrm{c}2} \left(0\right)$ at ambient pressure (AP). Our results reveal an extremely low-pressure coefficients of $T_{\mathrm{c}}$, i.e., $d{T}_c/dP\approx -0.047$ K/GPa for $P<15$ GPa and −0.017 K/GPa for $15<P<50$ GPa, presumably associated with an inherent large bulk modulus of $\sim 252$ GPa. Interestingly, we find that its $B_{\mathrm{c}2}$ $\left(0\right)$ undergoes a smooth crossover at 35.6 GPa from well beyond to less than the Pauli paramagnetic limit $B_{\mathrm{p}}^{\mathrm{BCS}}\left(0\right)=1.84T_c$; i.e., the $B_{\mathrm{c}2}\left(0\right)\approx 18.2 \mathrm{T}=1.7B_{\mathrm{p}}^{\mathrm{BCS}} \left(0\right)$ at AP decreases to $\sim 5.8 \mathrm{T}=0.88B_{\mathrm{p}}^{\mathrm{BCS}} \left(0\right)$ at 50 GPa. The density-functional calculations predict the possible occurrence of pressure-induced Fermi surface reconstruction for the energy bands near the $K$ point with strong spin-orbit coupling in 31–41 GPa. The present work sheds more light on this intriguing superconductor capable of resisting large external compression and strong magnetic fields.

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• Electrical properties
• Pressure effects
• Electronic structure
• Superconductors
• Density functional calculations