  We study a coupled quintessence model with pure momentum exchange and present
the effects of such an interaction on the Cosmic Microwave Background (CMB) and
matter power spectrum. For a wide range of negative values of the coupling
parameter $\beta$ structure growth is suppressed and the model can reconcile
the tension between Cosmic Microwave Background observations and structure
growth inferred from cluster counts. We find that this model is as good as
$\Lambda$CDM for CMB and baryon acoustic oscillation (BAO) data, while the
addition of cluster data makes the model strongly preferred, improving the
best-fit $\chi^2$-value by more than $16$.
