The Laves phase ZrZn₂ exhibits weak ferromagnetism at low temperatures that differs in many ways from the predictions of a weakly spin polarised Fermi liquid. Surprisingly, ZrZn₂ recently was even found to become superconducting in the milli-Kelvin temperature range. Ferromagnetism and superconductivity vanish above the same critical pressure p_c \approx 21 kbar, suggesting that itinerant ferromagnetism may be a precondition for the superconductivity.

PACS numbers: 71.27.+a, 72.80.Ga, 73.43.Nq, 74.20.Nm