where V represents the valence, e is the number of valence electrons, and b is the number of formed bonds, while c and a denote cations and anions, respectively. Each bond between anions or between cations reduces the magnitude of the valence by 1. Utilizing this charge counting method, the complex structure of Yb 14 M Sb 11 can be described as consisting of (M Sb 4 ) m-(m = 9 or 10) isolated tetrahedra, (Sb 3 ) 7-linear units, and isolated Yb 2+ and Sb 3-ions. The value of m depends on the valence of the atom on the M site. When M is trivalent, like Al 3+ , m = 9 and the compound is a valence balanced semiconductor. When M is divalent, like Mg 2+ , m = 10 and the compounds are slightly electron poor making a p-type metal or heavily doped semiconductor. This system of charge counting has enabled tuning of the free charge carrier concentration in A 14 M Sb 11 compounds by substituting some A and M atoms with others of a different valence Another way to understand the chemistry of the Zintl compounds is to combine the Zintl concept with molecular orbital analysis . This method has been successfully applied to half-Heusler compounds to interpret band structures based on the characteristics of molecular orbitals . The high symmetry of the clearly distinguished (M Sb 4 ) m-and (Sb 3 ) 7-structural units renders possibilities of identifying their molecular orbitals in the electronic structure to interpret the complex band structures.