We report the structural, magnetic, thermodynamic, and transport properties of EuRh2Ga8, EuRh2In8, and YbCo2Ga8. While the two former compounds show the onset of antiferromagnetic order at 20 and 5 K respectively, the latter remains nonmagnetic down to lowest temperatures. The electrical resistivity of the magnetic Eu-compounds is nearly unaffected by an external magnetic field, but the nonmagnetic YbCo2Ga8 develops a positive magnetoresistance.

A number of rare-earth alumo-silicides (R-Al-Si) have been synthesized from the corresponding elements by high-temperature reactions, carried out in excess of aluminum to serve as a flux. Under these experimental conditions, large single crystals of all R-Al-Si ternary phases were readily produced. The crystal structures these ternaries adopt were studied by means of powder and single-crystal X-ray diffraction and were classified as follows: (1) the early rare-earths (R=La, Ce, Pr, Nd, Sm, Gd) yield RAlxSi2-x, x∼1, non-stoichiometric ternary derivatives of the body-centered α-ThSi2-type; (2) the late rare-earths (R=Tb, Dy, Ho, Er, Tm) form stoichiometric R2Al3Si2 compounds that crystallize in the C-centered monoclinic Y2Al 3Si2-type; (3) the divalent Eu and Yb produce EuAl 2Si2 and YbAl2Si2 with the trigonal CaAl2Si2-type, whereas the last lanthanide element, Lu, forms LuAlSi with C-centered orthorhombic YAlGe-type. These structural trends are reviewed, and the evolution of the basic physical properties such as magnetism, heat capacity and electrical resistivity when moving across the series is described in detail. © 2005 Elsevier Inc. All rights reserved.

Magnetic susceptibility, heat capacity, and electrical resistivity measurements have been carried out on single crystals of the intermediate valence compounds Yb2 Rh3 Ga9 and Yb2 Ir3 Ga9. These measurements reveal a large anisotropy due apparently to an interplay between crystalline electric field (CEF) and Kondo effects. The temperature dependence of magnetic susceptibility can be modelled using the Anderson impurity model including CEF within an approach based on the non-crossing approximation. © 2005 The American Physical Society.