Interaction between positrons and chains of niobium atoms in Bn3Al

The effect of angular correlation of annihilation radiation (a.c.a.r.) has been investigated on polycrystalline samples of Nb3Al under various heat-treatment conditions. Measurements have been conducted with samples before and after their annealing. It is pointed out that the shape of the a.c.a.r. curve is influenced by the position of the Fermi surface in relation to the zone boundaries. Fermi level of d-electrons which are responsible for the ''one-dimensional'' properties of Nb3Al lies below the zone boundary, at a comparatively small distance from it (sigma approximately 0.17 π/a)