We report the first experimental observation of subgap transport in ferromagnetic insulator–superconductor–insulator–superconductor junctions realized in $\mathrm{EuS}/\mathrm{Al}/\mathrm{AlOx}/\mathrm{Al}$ vertical stacks. Differential conductance measurements reveal multiple Andreev reflection peaks, with odd-order peaks split by the spin-splitting induced in the superconductor adjacent to EuS, while even-order peaks remain unaffected. Combining experiments with quasiclassical transport modeling, we extract the spin-splitting and an approximate distribution of transmission channels, finding that roughly a hundred highly transmitting ($\tau >0.3$) channels will dominate transport. The observation of a Josephson current further confirms strong superconducting coupling through these channels. Our results demonstrate that a single spin-split superconductor is sufficient to observe the even-odd multiple Andreev reflection effect. Our work establishes EuS/Al junctions as a versatile platform to study subgap transport, Josephson coupling, and spin-polarized superconducting phenomena.

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• Andreev reflection
• Superconducting devices