A new compound composed of Nd, Fe, and a small quantity of B about 1 weight has been found, which has a tetragonal structure with lattice constants a = 0.880 nm and c = 1.221 nm. This phase, which has the approximate composition, 12 atom Nd, 6 atom B and balance Fe, possesses remarkable magnetic proper ties. From the approach to saturation an anisotropy con stant of about 3.5 MJ/m 3 can be calculated, while satura tion magnetization amounts to 1.35 T. The magnetiza tion versus temperature curve shows a Curie tempera ture of 585 K, which is much higher than those of the Fe and light rare earth binary compounds. Based on the new compound, sintered permanent magnets have been developed which have a record high energy product. Permanent magnet properties and physical properties of a typical specimen which has the composition Nd15B8Fe are as follows: Br = 1.23 T, HcB = 880 kA/m, HcI = 960 kA/ m, BH max = 290 kJ/m 3 , temperature coe cient of Br = 1260 ppm/K, density = 7.4 Mg/m 3 , specific resistivity = 1.4 μ m, Vickers hardness = 600, flexual strength = 250 MPa.