  Material challenges are the key issue in Majorana nanowires where surface
disorder constrains device performance. Here, we tackle this challenge by
embedding PbTe nanowires within a latticematched crystal, an oxide-free
environment. The wire edges are shaped by self-organized growth instead of
lithography, resulting in nearly-atomic-flat facets along both cross-sectional
and longitudinal directions. Quantized conductance plateaus are observed at
zero magnetic field with channel lengths reaching 1.54 $\mu$m, significantly
surpassing the state-of-the-art of III-V nanowires (nearly an
order-of-magnitude improvement compared to InSb). Coupling PbTe to a Pb film
unveils a flat interface spanning microns and a large superconducting gap of 1
meV. Our results meet the stringent low-disorder requirement for the definitive
observation of Majoranas.
