*2.1.2 Structural and physical properties of Pr*2*Ba*4*Cu*7*O*<sup>15</sup>*<sup>δ</sup> samples*

X-ray diffraction measurements on the produced samples were carried out at room temperature with an Ultima IV diffractometer (Rigaku) using Cu-K*α* radiation. We evaluated the lattice parameters from the x-ray diffraction patterns using the least-squares fits.

The local crystal structure of the Pr247 sample was revealed by high-resolution transmission electron microscopy (TEM) using a JEOL3010 microscope operated at 300 kV at Tohoku University, to examine alternative stacking along the *c*-axis between CuO single-chain and double-chain blocks. The electric resistivity as a function of temperature was measured by the *dc* four-terminal method using a Gifford-McMahon cryocooler (Sumitomo heavy Industries).

We performed Hall coefficient measurements on the 48-h-reduced samples with the five-probe technique using a physical property measuring system (PPMS, Quantum Design), to check the sign of carriers in the present Pr247 superconductor. For determination of an onset temperature of superconductivity and superconducting volume fraction at low temperatures, the *dc* magnetization was performed under zero-field cooling (ZFC) in a commercial superconducting quantum interference device (SQUID) magnetometer (MPMS, Quantum Design).
