  Fast, reversible, and low-power manipulation of the spin texture is crucial
for next generation spintronic devices like non-volatile bipolar memories,
switchable spin current injectors or spin field effect transistors.
Ferroelectric Rashba semiconductors (FERSC) are the ideal class of materials
for the realization of such devices. Their ferroelectric character enables an
electronic control of the Rashba-type spin texture by means of the reversible
and switchable polarization. Yet, only very few materials have been established
to belong to this class of multifunctional materials. Here, Pb1-xGexTe is
unraveled as a novel FERSC system down to nanoscale. The ferroelectric phase
transition and concomitant lattice distortion is demonstrated by temperature
dependent X-ray diffraction, and its effect on electronic properties are
measured by angle-resolved photoemission spectroscopy. In few nanometer-thick
epitaxial heterostructures, a large Rashba spin-splitting is exhibiting a wide
tuning range as a function of temperature and Ge content. Our work defines Pb1-
xGexTe as a high-potential FERSC system for spintronic applications.
