I shall review our recent proposal of the use of the harmonic-space cross-correlation power spectrum between the arrival directions of ultra-high energy cosmic rays (UHECRs) and the distributions of galaxies in the Universe, as observed by cosmological surveys of the large- scale structure (LSS). We expect the two observables to correlate, due to both galaxies and UHECR sources being hosted within dark matter haloes, which constitute the very LSS. This cross-correlation has not yet been considered in the literature. We formalise analytically such a cross-correlation and show how, if the distribution of UHECR sources traces indeed the LSS, the combination of auto- and cross-correlation greatly helps to detect UHECR anisotropies, even with current data. We show that the cross-correlation is more sensitive to UHECR anisotropies on small angular scales, more robust to systematic uncertainties, and it could be used to determine the redshift distribution of UHECR sources.