A combinatorial construction of an M12-invariant code

A ternary [66, 10, 36]3-code admitting the Mathieu group M12 as a group of automorphisms has recently been constructed by N. Pace, see [N. Pace: New ternary linear codes from projectivity groups, Discrete Mathematics 331 (2014), 22-26]. We give a construction of the Pace code in terms of M12 as well as a combinatorial description in terms of the small Witt design, the Steiner system S(5, 6, 12). We also present a proof that the Pace code does indeed have minimum distance 36.