Flux Crystal Growth of the RERuGe (RE = La, Ce, Nd, Gd, Tb) Series and Their Magnetic and Metamagnetic Transitions.

Previously synthesized only as powders, single crystals of the RERuGe (RE = La, Ce, Nd, Gd, Tb) series of compounds have now been obtained from molten In. These materials crystallize with the UCoSi-type structure in orthorhombic space group Ibam with lattice parameters a ≈ 10.00-9.77 Å (La-Tb), b ≈ 12.51-12.35 Å, and c ≈ 5.92-5.72 Å. The structure is a three-dimensional framework consisting of RuGe and RuGe units, as well as Ge-Ge zigzag chains. This structure type and those of the other five (ScFeSi, LuCoSi, YRhSn, YbIrGe, and YbPtSn) to compose the RETX phase space are discussed in depth. For the three compounds with RE = Nd, Gd, Tb, multiple magnetic transitions and metamagnetic behavior are observed. Electronic band structure calculations performed on LaRuGe indicate that these materials have a negative band gap and are semimetallic in nature.