  Effect of contact interfaces, between metallic single-wall carbon nanotubes
(SWCNT) and external electrodes made also of nanotubes, on the electrical
conductance is studied. A tight-binding model with both diagonal and
off-diagonal disorder, a recursive Green function technique as well as the
Landauer formalism are used. The studies are carried out within the coherent
transport regime and are focused on: (i) evolution from conductance
quantization to resonant tunneling, (ii) SWCNT's length effects and (iii)
magnetoresistance. It is shown that the so-called on-resonance devices, i.e.
nanotubes having a conductance peak at the Fermi energy, occur with a period of
3 carbon inter-ring spacings. Additionally, the present approach provides an
insight into magnetoresistance dependence of SWCNTs on conditions at the
contact interface.
