Singularity in the thermal boundary resistance between superfluid 4He and a solid surface -: art. no. 095702

We report new measurements in four cells of the thermal boundary resistance R between copper and He-4 below but near the superfluid-transition temperature T-lambda. For 10(-7) less than or equal to t = 1 - T/T-lambda less than or equal to 10(-4) fits of R = R(0)t(-xb) + R-B to the data yielded x(b) similar or equal to 0.18, whereas a fit to theoretical values based on the renormalization-group theory yielded x(b) = 0.23. Alternatively, a good fit of the theory to the data could be obtained if the amplitude of the prediction was reduced by a factor close to 2. The results raise the question whether the boundary conditions used in the theory should be modified.