CeCu₅Au is a stoichiometric compound derived from CeCu₆ by replacing the Cu(2) sites by Au. It orders antiferromagnetically at T_N ≈ 2.2 K. The (B, T) phase diagram of this compound for magnetic field parallel to the easy c direction reveals several phases, presumably two different antiferromagnetic phases and a spin-flop phase. The low-T specific heat (measured down to 80 mK) indicates that heavy-fermion behavior prevails in the presence of magnetic ordering.