Observation of a Narrow State Decaying into<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msubsup><mml:mrow><mml:mi>Ξ</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="normal">c</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:mrow><mml:mrow><mml:msup><mml:mrow><mml:mi>π</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>

Using data recorded by the CLEO-II detector at Cornell Electron Storage Ring (CESR), we report the first observation of a narrow state decaying into ${\ensuremath{\Xi}}_{c}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$. The state has mass difference $M({\ensuremath{\Xi}}_{c}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})\ensuremath{-}M({\ensuremath{\Xi}}_{c}^{+})$ of 178.2 \ifmmode\pm\else\textpm\fi{} 0.5 \ifmmode\pm\else\textpm\fi{} 1.0 MeV/${\mathit{c}}^{2}$, and a width of 5.5 MeV/${\mathit{c}}^{2}$ (90% confidence level limit). The most likely explanation of this new state is that it is the ${\ensuremath{\Xi}}_{c}^{*0}$, the ${J}^{P}={\frac{3}{2}}^{+}$ spin excitation of the ${\ensuremath{\Xi}}_{c}^{0}$ charmed baryon.