Mn 54 Al 44 C 2 ribbon samples have been prepared by melt spinning in a single-phase ɛ hexagonal disordered state and its exothermal transformation at around 500°C into a tetragonal L1 0 type magnetic structure (τ-phase) was followed by DTA, DSC, X-ray diffraction and thermomagnetic measurements. The metastable τ-phase stabilized by carbon addition could be transformed reversibly into the ɛ-phase at around 800°C, without decomposition into the stable Al 8 Mn 5 and β manganese phases. The almost constant Curie temperature obtained for partially transformed two-phase samples indicated a compositionally invariant transformation. By grinding the thin (25μm) ribbon into sub-millimeter flakes, a bulk anisotropic magnet could be compacted by magnetic field oriented powder technology.