Synthesis was carried out of REB 5 0 (RE=Tb,Dy) compounds which have a new 9th type of structure of the B 1 2 icosahedral compounds. Measurements of the static magnetic susceptibility of TbB 5 0 at high fields confirmed the antiferromagnetic-like transition previously observed. A similar magnetic transition was also observed for DyB 5 0 at 6.2K. The REB 5 0 -type compounds are the first higher borides in which a magnetic transition occurs. The difference in transition temperatures indicated that the length of the B 1 2 icosahedral axis cannot be the sole consideration of the magnetic interaction.