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We report the first contact-free measurements of the upper critical fields, ${\mathrm{H}}_{\mathrm{c}2}$(T), of single-crystal ${\mathrm{Y}}_{1}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{x}}$. In contrast to resistive measurements reported by others, we find that the anisotropy near ${\mathrm{T}}_{\mathrm{c}}$ is temperature independent in agreement with the expectations of anisotropic Ginzburg-Landau theory. Estimates of the anisotropic Ginzburg-Landau and London parameters are reported. These indicate that despite the large anisotropy in ${\mathrm{H}}_{\mathrm{c}2}$ (5:1), the inferred low-temperature interplanar coherence length (${\ensuremath{\xi}}_{\mathrm{z}}$=7 A\r{}) remains larger than the Cu-O layer spacing of 3.9 A\r{}. The superconductivity in ${\mathrm{Y}}_{1}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{x}}$ thus remains fundamentally three dimensional in nature for a substantial temperature range below ${\mathrm{T}}_{\mathrm{c}}$.

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