Results of the periodicity analysis on the polarisation fraction over time, selecting only data points that are physical, have an error bar smaller than 0.5, and have a flux density below 0.5 mJy to remove the bursts. Panel a: Lomb-Scargle periodogram of the polarisation fraction. The red line marks the rotation period of AU Mic (Plavchan et al. 2020). The orange line shows the Lomb-Scargle periodogram of the window function, scaled to fit the plot. Panel b: Circular polarisation fraction of emission as a function of phase. The colour scale represents the time of observing. The black data points show the binned data, where the bins are chosen such that each bin contains at least 7 data points. The red line shows a sine fit to the phase-folded data with a fixed period of 4.86 days, as discussed in Sect. 6.4. The zero point is arbitrary, set to the last observation in our campaign at MJD 60035.1.