The new binary intermetallic YbGe_2.83

The new compound YbGe_2.83 was obtained from the reaction of Yb and Ge in liquid indium. The crystal structure of YbGe_2.83 adopts the trigonal, P3m1 space group with a=b=8.3657(12) and c=7.0469(14) . The structure of YbGe_2.83 is a variant of the CaAl₂Si₂ structure type with ordered vacancies. Germanium atoms form double layers of puckered hexagons creating slabs that sandwich the Yb atoms. YbGe_2.83 can be classified as a Zintl compound with the formula Yb ^(2x)(Ge_2.83)^(2x)-. The deficiencies at the Ge sites cause a mixed/intermediate valent state of ytterbium (Yb^2.35). Valence bond sum calculations suggest an average valence of Yb ions in YbGe _2.83 of 2.51 consistent with an intermediate valence compound.