From Mach to July 2023, we had the pleasure to host Nicolas Fermon from Ecole National Supérieure (ENS) Paris-Saclay for his internship. As part of Anna Friedel’s work on highly polarized Heusler alloys, Nicolas studied their magneto-optical properties. He was able to show that the semimetal Co2MnSi, grown at the Institut Jean Lamour in Nancy, exhibits a large quadratic magneto-optic Kerr effect (Q-MOKE), which is an important step towards understanding the magnon dynamics in Co2MnSi when studied with Brillouin light scattering spectroscopy.