Two-dimensional (2D) angular correlation of annihilation radiation and Compton scattering are both powerful techniques to investigate the bulk electronic structure of crystalline solids through the momentum density of the electrons. Here we apply both methods to a single crystal of Pd to study the electron momentum density and the occupancy in the first Brillouin zone and to point out the complementary nature of the two techniques. To retrieve the 2D spectra from one-dimensional Compton profiles, a direct inversion method is implemented and benchmarked against the well-established Cormack's method. The comparison of experimental spectra with first-principles density functional theory calculations of the electron momentum density and the two photon momentum density clearly reveals the importance of positron probing effects on the determination of the electronic structure. While the calculations are in good agreement with the experimental data, our results highlight some significant discrepancies.

2D angular correlation of the positron annihilation radiation (2D‐ACAR) spectra are measured for LaB6 along high‐symmetry directions and compared with first‐principles calculations based on density functional theory (DFT). This allows the modeling of the Fermi surface in terms of ellipsoid electron pockets centered at X‐points elongated along the Σ axis (Γ−M direction). The obtained structure is in agreement with quantum oscillation measurements and previous band structure calculations. For the isostructural topologically nontrivial SmB6, the similar ellipsoids are connected through necks that have significantly smaller radii in the case of LaB6. A theoretical analysis of the 2D‐ACAR spectra is also conducted for CeB6 including the on‐site repulsion U‐correction to the local density approximation (LDA+U) of the DFT. The similarities of the 2D‐ACAR spectra and the Fermi surface projections of these two compounds allow to infer that both LaB6 and CeB6 are topologically trivial correlated metals.