Stabilization of New Forms of the Intermetallic Phases <i>β</i>-RENiGe₂ (RE = Dy, Ho, Er, Tm, Yb, Lu) in Liquid Indium

Flux conditions using liquid indium bypass the thermodynamically stable structure and yield new forms of the phases RENiGe2 (RE = Dy, Er, Yb, Lu). The compounds crystallize in the orthorhombic Immm space group and possess the YIrGe2 structure type. Lattice parameters for ErNiGe2, DyNiGe2, YbNiGe2, and LuNiGe2 are a = 4.114(1) Å, b = 8.430(2) Å, c = 15.741(5) Å; a = 4.1784(9) Å, b = 8.865(2) Å, c = 15.745(3) Å; a = 4.0935(6) Å, b = 8.4277(13) Å, c = 15.751(2) Å, and a = 4.092(1) Å, b = 8.418(3) Å, c = 15.742(5) Å, respectively. These phases represent a new structural arrangment (β) of the compound type RENiGe2 as another set of compounds with identical stoichiometry are known to adopt the orthorhombic Cmcm CeNiSi2 type structure (α). In this paper we report the crystal and electronic band structure of four new members of the YIrGe2 structure type, as well as an investigation of the relative thermodynamic stabilities of the two forms.