We have successfully synthesized a single-phase sample of double-chain PrBa2Cu4O8 at ambient oxygen pressure by employing the nitric pyrolysis method. Electrical resistivity, ac magnetic susceptibility, and neutron-diffraction measurements were performed to study the basic magnetic properties of the system. The system displayed metallic conduction, and no superconductivity was observed for temperatures down to 4.2 K. An anomaly was evident in the temperature dependence of the ac susceptibility around 200 K, where a shoulder in the resistivity was also clearly seen. The Pr spins were found to order at 17 K, with a magnetic structure that may be characterized by {1/2 1/2 l} wave vectors with l = whole integers and half integers, showing that the couplings between the Pr spins are antiferromagnetic in nature. Another transition of unknown origin is also evident around 2 K. [S0163-1829(99)03729-7].
