Possible canted antiferromagnetism in UCu9Sn4

We report on the new compound UCu9Sn4 which crystallizes in the tetragonal structure I4/mcm with lattice parameters a=8.600A and c=12.359A. This compound is isotyp to the ferromagnetic systems RECu9Sn4 (RE=Ce, Pr, Nd) with Curie temperatures TC=5.5, 10.5 and 15K, respectively. UCu9Sn4 exhibits an uncommon magnetic behavior resulting in three different electronic phase transitions. Below 105K the sample undergoes a valence transition accompanied by an entropy change of 0.5Rln2. At 32K a small hump in the specific heat and a flattening out in the susceptibility curve probably indicate the onset of helical spin-order. To lower temperatures a second transition to antiferromagnetic ordering occurs which develops a small ferromagnetic contribution on lowering the temperature further. These results strongly hinting for canted antiferromagnetism in UCu9Sn4