Ferromagnetism and antiferromagnetism have long been known to scientists as two classes of magnetic order of materials. Back in 2019, researchers postulated a third class of magnetism, called altermagnetism. This altermagnetism has been the subject of heated debate among experts ever since, with some expressing doubts about its existence. Recently, a team of experimental researchers was able to measure for the first time at DESY (Deutsches Elektronen-Synchrotron) an effect that is considered to be a signature of altermagnetism, thus providing evidence for the existence of this third type of magnetism.