Single crystal of erbium, ytterbium-codoped yttrium aluminum tetraborate Er,Yb:YAl3(BO3)(4)(Er,Yb:YAB) has been grown by the flux method. The absorption spectrum in the visible and NIR regions of Er,Yb:YAl3(BO3)(4) crystal are measured at room temperature and fluorescence spectrum of Er,Yb:YAl3(BO3)(4) crystal are also measured at room temperature, excited by 976 nm laser. Not only the strong NIR emission peaks located at 1548 nm was observed, but also the visible up-conversion luminescence has been found. The specific heat of the Er/Yb:YAB crystal at room temperature is 0.81 J/g degreesC. (C) 2004 Elsevier Ltd. All rights reserved.