Abstract
Muon spin rotation has been used to investigate the magnetic-field distribution in the vortex state of superconducting LuNi2B2C (T(c)approximate to16 K). Data for the magnetic field range 0.06H(c2)less than or similar toHless than or similar to0.23H(c2) are fitted to a nonlocal London model. The temperature dependence of the vortex core radius shows a clear Kramer-Pesch effect due to depopulation of bound states within the cores. Also, the penetration depth and core radius vary substantially with applied magnetic field, suggesting the presence of anomalous field-induced quasiparticles and vortex-vortex interactions.