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We show that prominent features in voltage-current characteristics, recently measured in the mixed state of high-Tc superconductors and interpreted as evidence for an irreversibility line or a vortexglass transition, may very well be explained with the simplest Kim-Anderson approach describing the vortex motion. In this case, the irreversibility line is not related to a transition in the system of vortices. Consulting numerous experimental reports on this subject we have not found a single example, which is in contradiction with this view.

Measurements of the magnetic field penetration depth in the ternary boride superconductor Li 2 Pd 3 B ͑T c Ӎ 7.3 K͒ have been carried out by means of muon-spin rotation ͑SR͒. The absolute values of , the Ginzburg-Landau parameter , and the first H c1 and second H c2 critical fields at T = 0 obtained from SR were found to be ͑0͒ = 252͑2͒ nm, ͑0͒ =27͑1͒, 0 H c1 ͑0͒ = 9.5͑1͒ mT, and 0 H c2 ͑0͒ = 3.66͑8͒ T, respectively. The zero-temperature value of the superconducting gap ⌬ 0 = 1.31͑3͒ meV was found, corresponding to the ratio 2⌬ 0 / k B T c = 4.0͑1͒. At low temperatures ͑T͒ saturates and becomes constant below T Ӎ 0.2T c , in agreement with what is expected for s-wave BCS superconductors. Our results suggest that Li 2 Pd 3 B is a s-wave BCS superconductor with only one isotropic energy gap.

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