  We report calculations of cosmic-ray proton, nuclei, antiproton, electron and
positron energy spectra within a "two-halo model" of diffusive transport. The
two halos represent a simple, physically consistent generalization of the
standard diffusion models, which assume a unique type of diffusion for cosmic
rays in the whole Galactic halo. We believe instead that cosmic rays may
experience a smaller energy dependence of diffusion when they are in proximity
of the Galactic disk. Our scenario is supported by recent observations of
cosmic-ray protons, nuclei, anisotropy, and gamma-rays. We predict remarkably
hard antiparticle spectra at high energy. In particular, at E>10 GeV, the
antiproton/proton ratio is expected to flatten, while the positron fraction is
found to increase with energy. We discuss the implications for cosmic-ray
physics and dark matter searches via antimatter.
