  We consider a $[ud]^2\bar{s}$ current, in the finite-density QCD sum rule
approach, to investigate the scalar and vector self-energies of the recently
observed pentaquark state $\Theta^+(1540)$, propagating in nuclear mater. We
find that, opposite to what was obtained for the nucleon, the vector
self-energy is negative, and the scalar self-energy is positive. There is a
substantial cancellation between them resulting in an attractive net
self-energy of the same order as in the nucleon case.
