First observation of the decay Ds+ → p(n)over-bar

Using e(+) e(-) -> D(s)(*-) D(s)(+) data collected near the peak D(s) production energy, E(cm) = 4170 MeV, with the CLEO-c detector, we present the first observation of the decay D(s)(+) -> p (n) over bar. We measure a branching fraction B(D(s)(+) -> p (n) over bar) = (1.30 +/- 0.36(-0.16)(+0.12)) x 10(-3). This is the first observation of a charmed meson decaying into a baryon-antibaryon final state.