  A Hopf algebra object in Loday and Pirashvili's category of linear maps
entails an ordinary Hopf algebra and a Yetter-Drinfel'd module. We equip the
latter with a structure of a braided Leibniz algebra. This provides a unified
framework for examples of racks in the category of coalgebras discussed
recently by Carter, Crans, Elhamdadi and Saito.
