New Intermetallics YbAu₂In₄ and Yb₂Au₃In₅

The intermetallic compounds YbAu(2)In(4) and Yb(2)Au(3)In(5) were obtained as single crystals in high yield from reactions run in liquid indium. Single crystal X-ray diffraction data of YbAu(2)In(4) showed that it crystallizes as a new structure type in the monoclinic space group P2(1)/m and lattice constants a = 7.6536(19) Å, b = 4.5424(11) Å, c = 9.591(2) Å and β = 107.838(4)°. The YbAu(2)In(4) compound is composed of a complex [Au(2)In(4)](3-) polyanionic network in which the rare-earth ions are embedded. Yb(2)Au(3)In(5) crystallizes in the polar space group Cmc2(1) with the Y(2)Rh(3)Sn(5) type structure and lattice constants a = 4.5351(9) Å, b = 26.824(5) Å, and c = 7.4641(15) Å. The gold and indium atoms define a complex three-dimensional [Au(3)In(5)] network with a broad range of Au-In (2.751(2) Å-3.0518(16) Å) and In-In (3.062(3) Å-3.3024(19) Å) distances. Magnetic susceptibility measurements of YbAu(2)In(4) revealed a transition at 25 K. Below the transition, the susceptibility of YbAu(2)In(4) follows Curie-Weiss behavior with an effective paramagnetic moment of 0.79 μ(B)/Yb. Magnetic susceptibility measurements on Yb(2)Au(3)In(5) show a mixed valent ytterbium and the magnetic moment within the linear region (<100 K) of 1.95 μ(B)/Yb. Heat capacity data for YbAu(2)In(4) and Yb(2)Au(3)In(5) give Debye temperatures of 185 and 153 K, respectively.