Muon tunneling along a ring-shaped orbit in UNi2Al3

The wave function of the implanted mu(+) in UNi2Al3 is found to be extended over a hexagonal ring of interstitial lattice sites m or k, closely surrou nding the highly symmetrical site b. This site assignment, inferred from th e angular dependence of high-field relaxation rates, leads to an equally co nsistent explanation of the medium- and low-field mu SR data. By using avai lable NMR data for the inherent 'crystal' electric field gradient (EFG), th e mu(+)-induced EFG at the Al nuclei could be determined. (C) 2000 Elsevier Science B.V. All rights reserved.