Spin splitting and even-odd effects in carbon nanotubes
  The level spectrum of a single-walled carbon nanotube rope, studied by transport spectroscopy, shows Zeeman splitting in a magnetic field parallel to the tube axis. The pattern of splittings implies that the spin of the ground state alternates by 1/2 as consecutive electrons are added. Other aspects of the Coulomb blockade characteristics, including the current-voltage traces and peak heights, also show corresponding even-odd effects. 
David H. Cobden, Marc Bockrath, Paul L. McEuen, Andrew G. Rinzler and   Richard E. Smalley