S1. Details of sample growth (Fig. S1)
S2. Sample characterization (Fig. S2-S5)
S3. Formation of a chemically abrupt interface (Fig. S6-S8)
S4. Detail of data analysis for resonant photoemission spectra (Fig. S9)
S5. Electronic structure of SrNbO3 films (Fig. S10-S13)
S6. Chemical state analysis for SrTiO3 surfaces (Fig. S14)
S7. Contribution of Sr cation to interfacial electronic states
References