Spectroscopic, transport, and magnetic results on the Nd/sub 2/minus//ital x//A/sub x//sup 4+/CuO/sub 4/minus//delta// systems (/ital A/=Ce and Th)

Structural, spectroscopic, transport, and magnetic results are presented for Nd/sub 2/minus//ital x//A/sub x//sup 4+/CuO/sub 4/minus//delta// materials with /ital A/=Ce and Th. The structural and spectroscopic results indicate a continuous evolution in properties up to the stability limit of /ital x/=0.2. In dramatic contrast, the superconducting properties are sharply peaked near /ital x/=0.16 where the system crosses over from semiconducting to metallic-type behavior.