Single-crystal study of the kagome antiferromagnet U3Ru4Al12

A ternary intermetallic compound, U3Ru4Al12 in a single-crystal form, was studied by measurement of susceptibility, magnetization, electrical resistivity, magnetoresistivity, thermopower, and heat capacity, as well as neutron diffraction, revealing that this aluminide is an antiferromagnetically ordered (T-N = 9.5 K) dense Kondo system (T-K approximate to 30 K) with a considerable enhancement of the Sommerfeld coefficient gamma(0) of about 200 mJ mol(U)(-1) K-2. The electrical resistivity and thermopower of U3Ru4Al12 show characteristic features of the interplay between anisotropic magnetic exchange, Kondo, and crystal field effects. A pronounced in-plane anisotropy and a unique noncollinear antiferromagnetic structure in the (a,b) hexagonal plane, found by neutron diffraction, are discussed in view of the effect of geometrical frustration caused by the distorted kagome lattice of a Gd3Ru4Al12-type crystal structure. Thus, the overall behavior of U3Ru4Al12 resembles that observed for the orthorhombic compound UCu5In, reported earlier as a spin density wave material.