Intermediate valence behaviour of Yb in a new intermetallic compound YbNi0.8Al4.2

We report on the valence band electronic structure as well as structural, magnetic and electronic transport properties of a novel intermetallic YbNi0.8Al4.2. The compound crystallizes in the orthorhombic YNiAl4-type structure (a = 4.049(2),b = 15.305(5) and c = 6.586(3) A) with space group Cmcm. The valence band spectrum and magnetic data indicate an intermediate valency of Yb ions in the studied compound with a valence of about 2.66 at room temperature. The temperature dependences of electrical resistivity, Hall effect and thermoelectric power display characteristic features of Kondo lattice with a large Kondo temperature (∼1300 K), being consistent with the intermediate valence scenario. An analysis of magnetic data suggests the presence of strong ferromagnetic correlations in the investigated compound at low temperatures. In order to obtain information about the electron-hole analogy between the Ce and Yb compounds, we have compared the observed behaviour with that of the dense Kondo compound CeNiAl4