  A diquark model is used to investigate single charmed baryons. In this model,
baryon is composed of two diquarks and an antiquark. Masses of lowest lying
states with $J^P= 1/2 ^ \pm$ are obtained. Some masses are smaller than other
theoretic predictions which indicates that these baryons of pentaquark
structure could be relatively stable. The results also show that
$\Lambda(2882)$ may be a pentaquark with $J^P=1/2^-$ and $\Xi(3125)$ may be a
pentaquark with $J^P=1/2^+$.
