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Spectroscopic evidence is given for the recurrent "domain phase" with oppositely magnetized regions in diamagnetic beryllium. A periodic splitting of the precession frequency of implanted muons in a Be single crystal was observed as the strength of the applied field H k ͗0001͘ varied near H 0 2.74 T. On sweeping H downwards, the doublet emerges and persists within more than one third of each de Haasvan Alphen cycle, the positions of the lines fixed, with the lower frequency (diamagnetic) component gaining and the higher (paramagnetic) one losing intensity. The line splitting gives DB ഠ 29 G for the induction difference in domains at T 0.8 K.

The local magnetic field in the bulk of superconducting single crystal ␤ tin was measured near and across the transition between the normal ͑N͒ and intermediate ͑I͒ state at Tϭ0.08 K. With varying applied field H a , the data indicate a reversible phase transition within the I state at H t Ϸ295 Oe, interpreted as a transition from the laminar to a tubular structure. Near the I→N transition, occurring at H cI ϭ0.98H c0 ϭ300 Oe, the field B in the N domains is strongly inhomogeneous with B ϽH c0 , it grows with the decrease of H a towards the value H c0 ϭ305.5Ϯ0.5 Oe. On lowering H a in the N state, a large ''field supercooling'' (␦H/H c Ϸ6%) of this state was observed.

The Fermi contact hyperfine contribution to the Knight shift of positive muons, implanted at the interstitial 3d sites in CeB6, is found to exhibit the same temperature dependence below T(Q) in phase II as the quadrupolar order parameter determined from resonant and nonresonant x-ray scattering. Furthermore, the contact coupling parameter is shown to be anisotropic and field dependent. These unanticipated features are interpreted to arise from the RKKY induced conduction electron spin polarization, which depends on the orientation and expectation value of the ordered 4f quadrupole moments.

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