Coexistence of metallic and nonmetallic charge transport inPrBa2Cu3O7

Magnetotransport measurements on highly oriented thin films of ${\mathrm{PrBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ demonstrate a unique coexistence of nonmetallic hopping conduction with metallic Boltzmann transport. At high temperature (T>10 K) hopping transport dominates, but when the inelastic conduction freezes out at low temperature, metallic behavior can be distinguished. The hopping conduction is assigned to the ${\mathrm{CuO}}_2$ planes, while the Boltzmann transport arises from the CuO chain structure, in agreement with recent electronic-structure calculations.