Two-dimensional angular correlation of (positron) annihilation radiation has been measured in the (100), (110), and (111) planes on a single crystal of ${\mathrm{CoSi}}_2$. A self-consistent linear-muffin-tin-orbitals band-structure calculation has been performed. Starting with this band structure, different models of annihilation enhancement and an electron-positron correlation potential were used to compute the two-photon momentum density. The comparison between theory and experiment at different stages of analysis is discussed for the various models. Generally speaking, the band-structure approach is found to be in very good agreement with experiment.

• Received 22 January 1991

DOI:https://doi.org/10.1103/PhysRevB.43.14532