A systematic study of the conductance of Y1-xPrxBa2Cu3O7/Pb planar tun
nel junctions as a function of Pr concentration, x, and crystallograph
ic orientation is presented. For fixed Pr concentration, the tunneling
conductance is the same when tunneling into (100)-, (110)-, and (103)
-oriented films, but qualitatively different than tunneling into (001)
-oriented films. In addition, the gap-like feature energy (similar to
2k(B)T(c)) scales with T-c, but only when tunneling in the ab-plane di
rection. An ongoing experiment characterizing a novel tunnel junction
fabrication technique using self-assembled monolayers as insulating tu
nnel barriers is also discussed.