Metallic Yb2AuGe3: An Ordered Superstructure in the AlB2‑Type Family with Mixed-Valent Yb and a High-Temperature Phase Transition

The intermetallic compound Yb2AuGe3 was synthesized from indium flux. Yb2AuGe3 crystallizes in the orthorhombic Ca2AgSi3-type structure which is an ordered superstructure of the AlB2 structure type. The structure was refined in the Fmmm space group with lattice parameters a = 8.5124(17) Å, b = 14.730(3) Å, c = 8.4995(17) Å. Temperature-dependent powder X-ray diffraction studies show that Yb2AuGe3 undergoes a phase transition from orthorhombic to hexagonal upon heating above 773 K. The compound shows weak paramagnetism that derives from a combination of Curie and Pauli paramagnetism with a magnetic moment value of 0.33(2) μB/Yb atom. Magnetic ordering was not observed down to 2 K. Yb2AuGe3 is metallic, and at low temperature the resistivity varies as T2, indicating possible Fermi liquid behavior. Heat capacity measurements suggest that Yb2AuGe3 is possibly a moderate heavy fermion system.