Motivated by the recent observation of ambient-pressure superconductivity with $T_c\approx 40\mathrm{K}$ in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ on ${\mathrm{SrLaAlO}}_4$(001) [Ko et al., Nature (London) 638, 935 (2025); Zhou et al., Nature (London) 640, 641 (2025)], we explore the structural and electronic properties as well as the spin-spin correlation function of this bilayer nickelate system by using density functional theory including a Coulomb repulsion term. We find that the compressive strain exerted by this substrate leads to an unconventional occupation of the antibonding Ni $3d_{z^2}$ states around the $\mathrm{\Gamma }$ point, distinct from the superconducting bulk compound under pressure. While pure strain effects rather modestly enhance the dynamical spin susceptibility, investigation of a reconstructed interface composition as observed in transmission electron microscopy uncovers a strong amplification of the spin fluctuations due to Fermi surface nesting of the antibonding Ni $3d_{z^2}$ states near the interface. These results provide insights into the emergence of superconductivity in strained ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$, suggest a possible key role of the interface, and highlight fundamental differences from the hydrostatic pressure scenario.

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• Electronic structure
• Epitaxial strain
• Superconductivity
• Nickelates
• Density functional theory