YbAuGeIn: An ordered variant of the YbAuIn structure exhibiting mixed-valent Yb behavior

YbAuGeIn was obtained as large single crystals in high yield from reactions run in liquid indium. Single crystal X-ray diffraction data show that YbAuGeIn is an ordered variant of YbAuIn with lattice constants, a = b = 7.3153(8) Å and c = 4.4210(5) Å, and space group P6̄2m. The parent compound YbAuIn was also studied for comparison. YbAuIn crystallizes in the ZrNiAl structure type, hexagonal, P6̄2m space group with lattice parameters a = b = 7.7127(11) Å and c = 4.0294(8) Å. In YbAuGe In, Ge substitutes for one of the two Au positions in the ternary compound YbAuIn. The structure can be described as alternating [GeIn] and [Yb Au] slabs that stack along the c-axis. The magnetic susceptibility data follow a modified Curie-Weiss law. The effective magnetic moment μ of 0.52 μ/Yb atom was deduced from the Curie constant and Curie-Weiss constant of θ =-1.5 K indicating antiferromagnetic interactions in YbAuGeIn. X-ray absorption near edge spectroscopy (XANES) measurements indicate intermediate valency for Yb in both compounds. The metallic nature of both compounds was confirmed by the resistivity measurements. Specific heat data for YbAuGeIn and YbAuIn give an electronic γ term of 31 and 84 mJ/mol·K, respectively, suggesting that the ternary analog is a "light" heavy fermion compound. © 2011 American Chemical Society.