The long-sought dice lattice flat band has recently been discovered for the first time in two-dimensional layered electride yttrium monochloride (YCl) [Geng et al., Nat. Commun. 17, 2213 (2026)]. While essential flat band features of YCl were captured by an idealized simple dice lattice model [Geng et al., Nat. Commun. 17, 2213 (2026)], we reveal in this Letter that a unique layer-orbital-valley coupling in YCl puts up a fundamental obstruction against a simple three-band dice lattice description of the flat band, and necessitates a multiorbital description that faithfully represents the symmetry, topology, and correlation physics in the first-ever dice metal. Using an ab initio–based multiorbital Hubbard model with local interactions, we predict that the multiorbital flat band supports a robust ferromagnetic ground state and electrically tunable correlated quantum anomalous Hall phases that are absent in an interacting single-orbital dice lattice. Our findings open a new avenue for exploring correlation and topology in electride systems.

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• Chemical Physics & Physical Chemistry
• Flat bands
• Magnetism
• Valley degrees of freedom
• Honeycomb lattice
• Lattices
• Layered crystals
• Topological materials
• Band structure methods
• Density functional calculations
• Hubbard model
• Materials modeling