  The mixing of photons with axion-like particles (ALPs) in the large-scale
magnetic field $B$ changes the polarization angle of a linearly polarized
photon beam from active galactic nuclei in radio galaxies as it propagates over
cosmological distances. Using available ultraviolet polarization data
concerning these sources we derive a new bound on the product of the photon-ALP
coupling $g_{a\gamma}$ times $B$. We find $g_{a\gamma} B \lesssim 10^{-11}$
GeV$^{-1}$ nG for ultralight ALPs with $m_a \lesssim 10^{-15}$ eV. We compare
our new bound with the ones present in the literature and we comment about
possible improvements with observations of more sources.
