A chemical intuition for the electronic structures of Yb 14 MgSb 11 and Yb 14 AlSb 11 described here can guide band engineering efforts of A 14 M X 11 compounds in general, as similar electronic structures have been observed in this class of materials. For example, charge density contour plots of the (As 3 ) 7-trimer unit in Ca 14 GaAs 11 are reminiscent of the molecular orbitals derived for the (Sb 3 ) 7-trimer in Figure . The antibonding σ * bands from the trimer unit is also observed in many compounds with the same structure type, regardless of whether the σ * bands are isolated from the other conduction bands (Ca ).