Specific energy loss of charged tracks in the TPC vs.\,rigidity ($p/z$) for Pb--Pb collisions at $\mathbf{\sqrt{{\textit s}_{\rm NN}}} = 5.02$ TeV. The dashed lines represent parameterisations of the Bethe--Bloch curve. Particles lighter than deuterons have been removed artificially, such that only nuclei are visible.