  The intracluster light (ICL) fraction, measured at certain specific
wavelengths, has been shown to provide a good marker for determining the
dynamical stage of galaxy clusters, i.e., merging versus relaxed, for small to
intermediate redshifts. Here, we apply it for the first time to a high-redshift
system, SPT-CLJ0615-5746 at z=0.97, using its RELICS (Reionization Lensing
Cluster Survey) observations in the optical and infrared. We find the ICL
fraction signature of merging, with values ranging from 16 to 37%. A careful
re-analysis of the X-ray data available for this cluster points to the presence
of at least one current merger, and plausibly a second merger. These two
results are in contradiction with previous works based on X-ray data, which
claimed the relaxed state of SPT-CLJ0615-5746, and confirmed the evidences
presented by kinematic analyses. We also found an abnormally high ICL fraction
in the rest-frame near ultraviolet wavelengths, which may be attributed to the
combination of several phenomena such as an ICL injection during recent mergers
of stars with average early-type spectra, the reversed star formation-density
relation found at this high redshift in comparison with lower-redshift
clusters, and projection effects.
