Zero-field muon-spin-resonance and lower-critical-field data are presented for a wide range of Th concentrations in Uix Th v Bei3, spanning the region where both a superconducting and a second, lowertemperature phase transition are observed. Overall T-x phase boundaries are assigned and discussed according to the nature of the lower phase transition. Arguments for associating the lower phase with a possible magnetic (time-reversal-violating) superconducting state are given.

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Muon spin depolarization has been studied in moderately concentrated AgMn and AuFe alloys from the freezing temperature T~up to 300 K. The muon depolarization function can be analyzed to show that the temperature dependence of the strongly nonexponential form of the local spin autocorrelation function in these canonical alloys is similar to that observed in numerical simulations on Ising spin glasses. The dynamic behavior above Tg appears to be an intrinsic precursor to spin glass freezing.

The behavior of the so-called weak moment antiferromagnetic states, observed in the heavy-fermion superconductors UPt 3 and URu 2 Si 2 , is discussed in view of recent µSR results obtained as function of control parameters like chemical substitution and external pressure. In UPt 3 , the Pd substitution for Pt reveals the dynamical character of the weak moment order. On the other hand, µSR measurements performed on samples in which Th substitutes U suggest that crystallographic disorder on the magnetic sites deeply affects the fluctuation timescale. In URu 2 Si 2 , a phase separation between the so-called hidden order state, present at ambient pressure, and an antiferromagnetic state, occurring under pressure, is observed. In view of the pressure-temperature phase diagram obtained by µSR, it is deduced that the respective order parameters have different symmetries.