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In 1996 the CCT initiated five key comparisons of realisations of the ITS-90 in various parts of the range. CCT-K1 concerns the range 0.65 K to 24.5561 K, where the ITS-90 is defined by specified vapour-pressure equations for 3He (0.65 K to 3.2 K) and 4He (1.25 K to 5.0 K) and by interpolation equations for a constant-volume gas thermometer (3 K to 24.5561 K). The transfer standards were rhodium–iron resistance thermometers calibrated by the seven participating laboratories. The report describes the comparison experiments, the results and uncertainties, and the calculation of interlaboratory equivalences. The comparison has been concluded by preparing an entry for Appendix B of the BIPM Key Comparison Database.Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

We have grown and investigated bulk single-crystal heavily boron-doped diamonds possessing superconductivity with . Only the surface layer with the thickness less than showed the degenerate semiconductor behavior with transition to the superconducting state, while the bulk of the crystal was a typical doped semiconductor. The morphology of the surface layer is dendritic polycrystalline with an average boron content of 2.5–2.9 at.%. The typical Josephson junction current-voltage characteristic was observed. The degenerate semiconductor-superconductor transition as in single-crystal high-temperature superconductors and the structural data analysis of the surface layer indicate the two-dimensional character of superconductivity, and the actual superconducting structure is a set of few-nanometer thick boron carbide layers embedded in a diamond structure.

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In 1964 the authors published preliminary results of their work on establishing the practical temperature scale in the temperature range from 4.2 K to 20 K [I].The temperature scale for this range W M d e k e d using a germanium resistance thermometer [2], as ita sensitivity and reproducibility of readings are as good BB it is required for the most accurate determinations of temperature.