New 4234-type Intermetallic Borocarbides: Synthesis, Structure, and Magnetic Properties

New 4234-type compounds, structurally related to the n=4 member of the (LnC)nNi2B2 homologous series of intermetallic borocarbides, were synthesized by arc-melting. Here we report that this structure type, previously observed only for Ni-based compounds, can be synthesized for a large number of transition elements. Further, we find it to be stable for medium through small lanthanides. The compounds have formulas Y4T2B3C4 [T=Fe, Co, Ni, Ru, Rh, and Ir], Ln4T2B3C4 [Ln=Er, Dy, and Gd; T=Fe and Co], Lu4Ni2B3C4, and Sc4Ni2B3C4. The unit cells are pseudo-tetragonal, with lattice parameters ranging from a= 3.348(1) ?, c=25.90(1) ? for Sc4Ni2B3C4 to a=3.624(1) ?, c=26.63(1) ? for Y4Rh2B3C4. Structural investigation by exitwave reconstruction is reported, showing the presence of twinning on the unit cell scale. The phases show either Curie– Weiss behavior with very small magnetic moments per transition metal atom or temperature-independent paramagnetism.