Temporal evolution of the longitudinal magnetic field for EV Lac. The shape of the data points distinguishes optical (circles) from near-infrared (squares), and the colour represents the epoch in which the data were collected. Top: full time series of measurements with ESPaDOnS, NARVAL, and SPIRou. Bottom: phase-folded curves of SPIRou data points colour-coded by epoch; the associated least-squares sine fits are shown as dashed lines. The rotation period used is listed in Table 1.