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We report results of magnetization and 19F NMR measurements in the normal state of as-grown vacuum-annealed LaO0.5⁢F0.5⁡BiS2. The magnetization is dominated by a temperature-independent diamagnetic component and a field- and temperature-dependent paramagnetic contribution 𝑀𝜇⁡(𝐻,𝑇) from a ∼1000 ppm concentration of local moments, an order of magnitude higher than can be accounted for by measured rare-earth impurity concentrations. 𝑀𝜇⁡(𝐻,𝑇) can be fit by the Brillouin function 𝐵𝐽⁡(𝑥) or, perhaps more realistically, a two-level tanh⁡(𝑥) model for magnetic Bi 6⁢𝑝 ions in defect crystal fields. Both fits require a phenomenological Curie-Weiss argument 𝑥=𝜇eff⁢𝐻⁡/(𝑇+𝑇𝑊), 𝑇𝑊≈1.7 K. There is no evidence for magnetic order down to 2 K, and the origin of 𝑇𝑊 is not clear. 19F frequency shifts, linewidths, and spin-lattice relaxation rates are consistent with purely dipolar 19F/defect-spin interactions. The defect-spin correlation time 𝜏𝑐⁡(𝑇) obtained from 19F spin-lattice relaxation rates obeys the Korringa relation 𝜏𝑐⁢𝑇=const, indicating the relaxation is dominated by conduction-band fluctuations. 

We have measured the superconducting penetration depth (T ) in the heavy-fermion/intermediate-valent superconducting alloy series Ce1−xYbxCoIn5 using a transverse-field muon spin relaxation to study the effect of intermediate-valent Yb doping on Fermi-liquid renormalization. From (T ) we determine the superfluid density ρs (T ) and find that it decreases continuously with increasing nominal Yb concentration x, i.e., with increasing intermediate valence. The temperature-dependent renormalization of the “normal” fluid density ρN (T ) = ρs (0) − ρs (T ) in both the heavy-fermion and intermediate valence limits is proportional to the temperature-dependent renormalization of the specific heat. This indicates that the temperature-dependent Fermiliquid Landau parameters of the superconducting quasiparticles entering the two different physical quantities are the same. These results represent an important advance in understanding of both intermediate valence and heavy-fermion phenomena in superconductors.