Wikipedia
Alpha-Naphthylthiourea
α-Naphthylthiourea (ANTU) is an organosulfur compound with the formula CHNHC(S)NH. This a white, crystalline powder although commercial samples may be off-white. It is used as a rodenticide and as such is fairly toxic. Naphthylthiourea is available as 10% active baits in suitable protein- or carbohydrate-rich materials and as a 20% tracking powder.