Systematic evolution of superconducting pairing strength and Seebeck coefficients in correlated infinite-layer La _{1– <i>x</i>} Sr <i> _x </i> NiO ₂

The recently found superconducting infinite-layer nickelates offer a unique platform to explore an exotic pairing mechanism in multiband systems toward high-temperature superconductivity and associated rich quantum phases, contrasting with cuprates. Here, we show that infinite-layer (La,Sr)NiO₂ exhibits strong-coupling superconductivity, resilient to in-plane magnetic fields exceeding 47 tesla at optimal doping-more than twice the Pauli limit for conventional Bardeen-Cooper-Schrieffer superconductors. This violation becomes pronounced toward the underdoped regime, implying an intriguing evolution of pairing glue. The unexpected observation of positive Seebeck coefficients in this regime indicates the presence of nontrivial electron correlations. Furthermore, our comprehensive investigation across the superconducting dome reveals that the evolution of (thermo)electric normal-state properties-specifically, the sign changes of the Hall and Seebeck coefficients-coincides with the evolution of superconducting anisotropy and pairing strength. This demonstrates a definitive link between electron correlations and strong-coupling superconductivity in (La,Sr)NiO₂, contributing to a unified framework for understanding unconventional superconductivity.