Ac susceptibility studies of a superconducting gallium nanocomposite: Crossover in the upper critical field line and activation barriers Evidence that the upper critical field of Nb3Sn is independent of whether it is cubic or tetragonal Appl. Phys. Lett. 99, 122507 (2011); 10.1063/1.3643055Quasiperiodic superconducting V/Zr multilayers: critical magnetic fields and crossover Low Temp.The arc-discharge process is usually used to synthesize some kinds of metal nanocrystals or nanoparticles all with high melting temperature. Here, the carbon-coated Sn ͑with a low melting temperature͒ nanostructured materials with different shapes, such as carbon-coated Sn nanorods with diameter of about 100 and 50 nm and, correspondingly, the length of 500 and 200 nm, and the carbon-coated Sn nanoparticles, are prepared by a modified arc-discharge process. The carbon shells are found to surround these Sn nanostructures. The carbon shell becomes thick with decreasing the size of the Sn nanostructures. The magnetic and electrical transports are affected by the shape of nanocrystals. The critical magnetic field of the carbon-coated Sn nanorods with diameter of 50 nm and length of 200 nm is almost 25 times higher than that of bulk Sn. The superconductivity of the carbon-coated Sn nanoparticles with particle size of 40 nm is destroyed. The zero bias tunneling anomalies was observed in the carbon-coated Sn nanoparticles.