Stabilization of New Forms of the Intermetallic Phases β-RENiGe ₂ (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 YlrGe₂ structure type. Lattice parameters for ErNiGe ₂, 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 YlrGe₂ structure type, as well as an investigation of the relative thermodynamic stabilities of the two forms.