  Strongly correlated materials feature multiple electronic orbitals which are
crucial to accurately understand their many-body properties, from cuprate
materials to twisted bilayer graphene. In such multi-band models, quantum
interference can lead to dispersionless bands whose large degeneracy gives rise
to itinerant magnetism even with weak interactions. Here, we report on
signatures of a ferrimagnetic state realized in a Lieb lattice at half-filling,
characterized by antialigned magnetic moments with antiferromagnetic
correlations, concomitant with a finite spin polarization. We demonstrate its
robustness when increasing repulsive interactions from the non-interacting to
the Heisenberg regime, and study its emergence when continuously tuning the
lattice unit cell from a square to a Lieb geometry. Our work paves the way
towards exploring exotic phases in related multi-orbital models such as quantum
spin liquids in kagome lattices and heavy fermion behavior in Kondo models.
