The common image which most people associate to magnetism is that of a compass needle: a small piece of lodestone which – when left free to rotate – aligns in the direction of the Earth's magnetic field, and which for many centuries helped countless navigators and explorers find their way. Today magnetic materials, apart from being ubiquitous on our refrigerators, are crucially important in a wide range of applications, from computer memories and hard drives to medical diagnostic techniques. However, the onset of superparamagnetism is a significant obstacle to the miniaturization of such devices: when the magnetic particle size becomes mesoscopic, the magnetization can be randomly flipped by thermal disorder even below Tc. In an effort to overcome this problem, Sessoli et al. reported the first example of magnetic bistability of molecular origin in a manganese-based cluster in 1993. Twenty years later, after a large number of molecular magnets based on transition metals, rare earths, and the actinide elements U and Np have been reported, we expanded this range of elements towards the frontier of the periodic table by discovering slow magnetic relaxation in a plutonium-based complex. ; JRC.G.I.5-Advanced Nuclear Knowledge