Tb Ni2 Mn is a cubic Laves material, isostructural to Tb Ni2, with the Mn sitting on both the Tb and the Ni lattice positions. It is ferromagnetic at ambient pressure at TC =151 K and has been investigated in detail at ambient pressure through magnetization and specific heat with various applied magnetic fields. It displays Curie-Weiss behavior above TC, with an effective moment of 8.43 μB f.u., and isothermal magnetization at various temperatures is consistent with narrow domain walls. The low-temperature specific heat results in a linear contribution of 65 mJ mol K2 and a Debye temperature of θD =188 K. The ac magnetic susceptibility has been investigated using designer diamond anvils up to 28.3 GPa. A magnetic anomaly at T* is investigated as a function of both magnetic field and pressure, both of which have very little effect for fields less than the coercive force. The Curie temperature decreases at a rate of d TC dP=-1.96 K GPa, and differences between hydrostatic and nonhydrostatic conditions are discussed. © 2007 The American Physical Society.