Thermal conductivity and superconductivity in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">Eu</mml:mi><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ba</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>7</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>

We have measured the thermal conductivity $\ensuremath{\kappa}$ from 2 to 200 K in the superconducting ceramic $\mathrm{Eu}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}x}$ observing an anomaly at the superconducting transition temperature ${T}_{c}$. Using general arguments and approximations, and supposing that the electrical resistivity is due to electron-phonon interaction, we separate quantitatively the different contributions to $\ensuremath{\kappa}$. The "observed" electron-limited phonon conductivity fairly follows the Bardeen-Rickayzen-Tewordt theory and a Bardeen-Cooper-Schrieffer-like energy gap with $\frac{2\ensuremath{\Delta}(0)}{{k}_{B}{T}_{c}}=3.3\ifmmode\pm\else\textpm\fi{}0.7$, in agreement with published data from other kinds of measurements.

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