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There have been several reports of a detection of an unexplained excess ofX-ray emission at $\simeq$ 3.5 keV in astrophysical systems. One interpretationof this excess is the decay of sterile neutrino dark matter. The mostinfluential study to date analysed 73 clusters observed by the XMM-Newtonsatellite. We explore evidence for a $\simeq$ 3.5 keV excess in the XMM-PNspectra of 117 redMaPPer galaxy clusters ($0.1 < z < 0.6$). In our analysis ofindividual spectra, we identify three systems with an excess of flux at$\simeq$ 3.5 keV. In one case (XCS J0003.3+0204) this excess may result from adiscrete emission line. None of these systems are the most dark matterdominated in our sample. We group the remaining 114 clusters into fourtemperature ($T_{\rm X}$) bins to search for an increase in $\simeq$ 3.5 keVflux excess with $T_{\rm X}$ - a reliable tracer of halo mass. However, we donot find evidence of a significant excess in flux at $\simeq$ 3.5 keV in any$T_{\rm X}$ bins. To maximise sensitivity to a potentially weak dark matterdecay feature at $\simeq$ 3.5 keV, we jointly fit 114 clusters. Again, nosignificant excess is found at $\simeq$ 3.5 keV. We estimate the upper limit ofan undetected emission line at $\simeq$ 3.5 keV to be $2.41 \times 10^{-6}$photons cm$^{-2}$ s$^{-1}$, corresponding to a mixing angle of$\sin^2(2\theta)=4.4 \times 10^{-11}$, lower than previous estimates fromcluster studies. We conclude that a flux excess at $\simeq$ 3.5 keV is not aubiquitous feature in clusters and therefore unlikely to originate from sterileneutrino dark matter decay.

The XMM Cluster Survey: new evidence for the 3.5 keV feature in clusters is inconsistent with a dark matter origin