Flux Crystal Growth of the RE 2 Ru 3 Ge 5 (RE = La, Ce, Nd, Gd, Tb) Series and Their Magnetic and Metamagnetic Transitions.

Previously synthesized only as powders, single crystals of the RE2 Ru3 Ge5 (RE = La, Ce, Nd, Gd, Tb) series of compounds have now been obtained from molten In. These materials crystallize with the U2 Co3 Si5 -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 RuGe5 and RuGe6 units, as well as Ge-Ge zigzag chains. This structure type and those of the other five (Sc2 Fe3 Si5 , Lu2 Co3 Si5 , Y2 Rh3 Sn5 , Yb2 Ir3 Ge5 , and Yb2 Pt3 Sn5 ) to compose the RE2 T3 X5 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 La2 Ru3 Ge5 indicate that these materials have a negative band gap and are semimetallic in nature.