A Tale of Two Polymorphs – Growth and Characterization of α‐LnNiGa 4 (Ln = Y, Gd–Yb) and β‐LnNi 1– x Ga 4 (Ln = Tb–Er)

The single crystals of two polymorphs of LnNiGa 4 , namely, the orthorhombic α‐LnNiGa 4 (Ln = Y, Gd–Yb) and, a new polymorph, the tetragonal β‐LnNi 1– x Ga 4 (Ln = Tb–Er), were successfully grown by using the self‐flux method. α‐LnNiGa 4 (Ln = Y, Gd–Yb) is isostructural to YNiAl 4 and can be described as an edge‐sharing polyhedral of Ni@Ga 7 Ln 2 (Ln = Y, Gd–Yb) along the ac ‐plane that is sandwiched between the square nets of the Ga atoms along the b ‐axis. The structure of β‐LnNi 1– x Ga 4 (Ln = Tb–Er) is a distorted variant of the Ce 2 NiGa 10 ‐structure type with a Ni deficiency and multiple Ga split positions and is structurally related to YNiGa 3 Ge. The magnetic data for β‐LnNi 1– x Ga 4 (Ln = Tb–Er) and the transport properties for α‐LnNiGa 4 (Ln = Y, Gd–Tm) and β‐LnNi 1– x Ga 4 (Ln = Tb–Er) are reported. Antiferromagnetic correlations are observed in the magnetic susceptibility of β‐LnNi 1– x Ga 4 (Ln = Tb–Er), where the magnetic transitions occurred below 7 K and with effective moments that are consistent with free Ln 3+ ions.