Metallic resistivity in crystalline ropes of single-wall carbon nanotubes

Laser ablation of (Co,Ni)-doped graphite yields {approximately} 70{percent} single-wall nanotubes, predominantly (10,10) armchair tubes which self-organize into crystalline {open_quotes}ropes{close_quotes}{gt}100 {Angstrom} in diameter and{gt}10 {mu}m long. We find {rho}{sub {parallel}}=0.03{minus}0.10m{Omega} cm at 300 K, with positive (negative) d{rho}/dT above (below) T{sup {asterisk}} = 35 K. Unoriented bulk samples exhibit similar behavior, with higher (directionally averaged) resistivities and T{sup {asterisk}}`s. The high-T behavior is consistent with the predicted intrinsic metallic state for this structure. {copyright} {ital 1997} {ital The American Physical Society}