  We report on the electronic properties of an artificial system obtained by
the intercalation of equiatomic FeCo layers under graphene grown on Ir(111).
Upon intercalation, the FeCo film grows epitaxially on Ir(111), resulting in a
lattice-mismatched system. By performing Density Functional Theory
calculations, we show that the intercalated FeCo layer leads to a pronounced
corrugation of the graphene film. At the same time, the FeCo intercalated
layers induce a clear transition from a nearly undisturbed to a strongly
hybridized graphene {\pi}-band, as measured by angle-resolved photoemission
spectroscopy. A comparison of experimental results with the computed band
structure and the projected density of states unveils a spin-selective
hybridization between the {\pi} band of graphene and FeCo-3d states. Our
results demonstrate that the reduced dimensionality, as well as the
hybridization within the FeCo layers, induce a narrowing and a clear splitting
of Fe 3d-up and Fe 3d-down spin bands of the confined FeCo layers with respect
to bulk Fe and Co.
