Abstract

We report the coexistence of ferromagnetic order and superconductivity in UCoGe at ambient pressure. The data obtained from the basic thermal, magnetic and transport properties on the macro and microscopic scale show that UCoGe is a weak ferromagnet with a Curie temperature TC = 3 K, and also, is a superconductor with a resistive transition temperature Ts = 0.8 K. Those present evidence that UCoGe is an unconventional superconductor and argue that superconductivity is mediated by critical ferromagnetic spin fluctuations.