Zero bias conductance peak (ZBCP) is known to occur in junctions between normal metal and conventional superconductor. This phenomenon is conventionally explained by Andreev reflection of the tunneling electrons at the interface and the ZBCP

normal metal and conventional superconductor. This phenomenon is conventionally explained by Andreev reflection of the tunneling electrons at the interface and the ZBCP height is limited to less than double of the normal conductance at higher bias. However, BSCCO is different from other conventional superconductors because of the d-wave characteristics of the order parameter. There are several theories describing the effect of Andreev reflection at the surface of a d-wave superconductor. One common feature of these theories is that the ZBCP can be enhanced dramatically (theoretically a singularity) because of the interference effect between order parameters of opposite signs in a d-wave superconductor. We have prepared BSCCO/Pb planar junctions and performed careful measurements on many of these junctions to demonstrate that the ZBCP in some of these junctions can indeed be as high as predicted by the theories. Planar junction instead of scanning tunneling microscope (STM) is used in this experiment because we want to study the temperature and magnetic field dependence of the ZBCP from the same junction. STM is in general unstable against changes in temperature and external field. It is necessary to withdraw and re-approach for another junction as temperature or field is changed.