  We report the magnetotransport and $dc$ magnetic susceptibility of the
polycrystalline samples of Pr$_{2}$Ba$_{4}$Cu$_{7}$O$_{15-\delta}$, to examine
the effect of magnetic field on the superconducting phase of the metallic CuO
double chain. The resistive critical magnetic field is estimated to be about 21
T at low temperatures from the resistive transition data. On the other hand,
the corresponding critical field determined from the magnetization measurements
gives rise to a very low value of $\sim 0.3$T at 2 K. These discrepancies in
the magnetic response between the resistivity and magnetization data are caused
by disappearance of the magnetically shielding effect even in relatively lower
fields. In spite of the observation of the resistive drop associated with the
superconducting transport currents, the suppression of the diamagnetic signal
is probably related to the superconductivity of quasi one-dimensional CuO
double-chain. The behavior of Seebeck coefficient in the superconducting
Pr$_{2}$Ba$_{4}$Cu$_{7}$O$_{15-\delta}$ is discussed on the basis of the double
chain model from the density functional band calculation.
