  We investigate the vacuum polarization effects associated with a charged
massless spin-1/2 field in a higher-dimensional space-time, induced by a
composite topological defect. The defect is constituted by a global monopole
living on a three-brane and two-dimensional conical space transverse to the
latter. In addition, we assume the presence of an extra magnetic flux along the
core of the conical space. The heat kernel and the Feynman Green function are
presented in the form of a sum of two terms. The first one corresponds to the
contribution coming from the bulk with global monopole in the absence of
conical structure of the orthogonal two-space, and the second one is induced by
this structure and the magnetic flux. We explicitly evaluate the part in the
vacuum expectation value of the energy-momentum tensor induced by the flux
carrying conical structure. As in pure cosmic string geometries, only the
fractional part of the ratio of the magnetic flux to flux quantum leads to
non-trivial effects. The vacuum energy-momentum tensor is an even function of
this parameter. We show that for strong gravitational fields corresponding to
large values of the solid angle deficit, the effects induced by the conical
structure and flux are exponentially suppressed.
