The　complex　polymer　[{Cu2L(pyca)　(H2O}n][ClO4]n·2nH　2O　[H2L　=　N,N′-bis(2-ammoethyl)oxamide.　Hpyca　=　pyridine-4-carboxylic　acid]　has　been　prepared　and　its　magnetic　properties　and　crystal　structure　determined.　The　crystals　are　monoclinic,　space　group　P21/c,　with　3　=　10.420(2),　b　=　13.118(2),　c　=　14.863(5)　Å,　β　=　93.05(2)°,　and　Z　=　4.　The　structure　consists　of　a　two-dimensional　network　of　copper(II)　ions　bridged　by　the　bis(tridentate)　ligand　L　in　trans　conformation,　and　by　pyridine-4-carboxylate　where　the　carboxylate　group　is　bonded　to　three　different　copper　centres　in　a　novel　manner.　The　repeating　asymmetric　unit　is　a　binuclear　copper(II)　fragment　with　one　of　the　metal　centres　in　an　octahedral　environment　whereas　the　other　is　in　a　distorted　square-based　pyramidal　geometry.　From　magnetic　susceptibility　measurements　the　complex　was　found　to　exhibit　a　strong　antiferromagnetic　coupling　with　J　=　-486　cm　-1　and　θ　=　-15　K,　due　to　the　efficiency　of　the　oxamidate　and　triatomic　anti-anti　carboxylate　bridges　in　propagating　antiferromagnetic　exchange　interaction　between　the　copper(II)　ions　which　are　separated　by　about　5.2　and　6.9　Å,　respectively.