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Gd 3 Co 11- x Ni x B 4 compounds, with x ≤ 6, were investigated by X-ray diffraction and magnetic measurements. The structural results show anisotropic variations of the lattice constants and a threshold Ni content is observed, x 2 3, in the composition dependence of the asymmetry parameter. The Curie temperatures and mean cobalt moments decrease as an effect of the cobalt substitution. The GdCo intersublattice exchange coupling estimated in the molecular field approximation shows a small composition dependence. Analyses of the experimental magnetic data obtained at saturation as well as in the paramagnetic temperature ranges indicate an increasing degree of itineracy of cobalt magnetic moments as the nickel content increases. Based on previous results for the values of local cobalt moments in R n + 1 Co 3 n + 5 B 2 n compounds, a preferential distribution of Ni at the Co lattice sites is suggested.

We present results of magnetisation, resistivity, thermopower and thermal conductivity measurements on the compound Eu 0.83 Fe 4 Sb 12 , which orders magnetically below 84 K. An interesting feature of this compound is the large positive magnetoresistance, reaching values of 130% at 2 K and 12 T, and still 30% at room temperature. Fe/Co substitution causes a drop in the magnetic ordering temperature T mag and an increase of the thermopower values, which is expected from a decrease of the charge carrier density.

A study of the pressure response of single-crystalline Fe 1− x Si 1+ x samples revealed a pressure-driven reduction of the band gap E g at high temperatures. Pressure also significantly changes the variable range hopping regime by lowering the electronic density of states at the Fermi energy.