First Observation of the Decay D{sub s}{sup +}{yields}pn

Using e{sup +}e{sup -}{yields}D{sub s}*{sup -}D{sub s}{sup +} data collected near the peak D{sub s} production energy, E{sub cm}=4170 MeV, with the CLEO-c detector, we present the first observation of the decay D{sub s}{sup +}{yields}pn. We measure a branching fraction B(D{sub s}{sup +}{yields}pn)=(1.30{+-}0.36{sub -0.16}{sup +0.12})x10{sup -3}. This is the first observation of a charmed meson decaying into a baryon-antibaryon final state.