A remarkable new electronic ground-state of a high-temperature superconductor oxide (YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7−δ</sub>) is found when it is grown in-between layers of a specific manganite (Pr<sub>0.5</sub>La<sub>0.2</sub>Ca<sub>0.3</sub>MnO<sub>3</sub>). The superconductor in these ‘superconductor sandwiches’ apparently adopts an exotic granular-state due to an interaction with the manganite. Uniquely, a strong magnetic field recovers a more ‘customary’ superconducting state. Here we show how Raman spectroscopy, state-of-the-art THz ellipsometry, and transport measurements are being used to reveal the nature of this new ground-state. These measurements are shedding light on how the manganite and superconductor layers interact to cause such novel behaviour, however the exact mechanism remains unknown.