becomes superconducting just below 40 K. Whereas porous polycrystalline samples of can be synthesized from boron powders, in this Letter we demonstrate that dense wires of can be prepared by exposing boron filaments to Mg vapor. The resulting wires have a diameter of , are better than dense, and manifest the full shielding in the superconducting state. Temperature-dependent resistivity measurements indicate that is a highly conducting metal in the normal state with . By using this value, an electronic mean-free path, can be estimated, indicating that wires are well within the clean limit. , , and data indicate that manifests comparable or better superconducting properties in dense wire form than it manifests as a sintered pellet.
- Received 12 February 2001
- Published in the issue dated 12 March 2001
© 2001 The American Physical Society