Investigation of the Electronic Structure of Uranium Compounds UX2 (X Pnigogen) and UAsY (Y Chalcogen) by Positron Annihilation

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Abstract
The electron momentum density distributions ϱ(p) in USb2, UP2, and UAsS are calculated for various sets of lattice harmonics Fϱ, using Mijnarends's method. The selection of the adequate set of harmonics is made by a comparison of the anisotropic parts of ϱ(p) with “difference” momentum density distributions ϱr(p) obtained on the basis of the difference angular correlation of positron annihilation quanta curves. From “summed up” distributions ϱs(p) = ϱpoly(p)+ ϱr(p) Fermi momenta along different directions are estimated. The character of the Fermi momenta changes suggests an ellipsoidal shape of Fermi surface, which corresponds to extremely large anisotropy of electric conductivity along [001] and [100] directions of the tetragonal unit cell of these compounds.