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Radial substructure in the form of rings and gaps has been shown to beubiquitous among protoplanetary discs. This could be the case in exoKuiperbelts as well, and evidence for this is emerging. In this paper we present ALMAobservations of the debris/planetesimal disc surrounding HD 206893, a systemthat also hosts two massive companions at 2 and 11 au. Our observations reveala disc extending from 30 to 180 au, split by a 27 au wide gap centred at 74 au,and no dust surrounding the reddened brown dwarf (BD) at 11 au. The gap widthsuggests the presence of a 0.9 M$_\mathrm{Jup}$ planet at 74 au, which would bethe third companion in this system. Using previous astrometry of the BD,combined with our derived disc orientation as a prior, we were able to betterconstrain its orbit finding it is likely eccentric ($0.14^{+0.05}_{-0.04}$).For the innermost companion, we used RV, proper motion anomaly and stabilityconsiderations to show its mass and semi-major axis are likely in the range4-100 M$_\mathrm{Jup}$ and 1.4-4.5 au. These three companions will interact onsecular timescales and perturb the orbits of planetesimals, stirring the discand potentially truncating it to its current extent via secular resonances.Finally, the presence of a gap in this system adds to the growing evidence thatgaps could be common in wide exoKuiper belts. Out of 6 wide debris discsobserved with ALMA with enough resolution, 4-5 show radial substructure in theform of gaps.

Insights into the planetary dynamics of HD 206893 with ALMA