  Models with pure momentum exchange in the dark sector have been shown to
provide a promising scenario to tackle the tension in the clustering inferred
from high- and low-redshift probes. A distinctive feature of these models is
that only the Euler equation for the dark matter component is modified and the
correction is such that the net effect can be associated to an additional
friction determined by the interaction rate. In this work, we show that the
strength of the interaction parameter needed to resolve the $\sigma_8$ tension
could be detected from the dipole of the matter power spectrum that is expected
to be measured in upcoming surveys.
