Anomalous enhancement of upper critical field in Sr2RuO4 thin films

We report large enhancement of upper critical field ${H}_{\mathrm{c}2}$ observed in superconducting ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}$ thin films. Through dimensional crossover approaching two dimensions, ${H}_{\mathrm{c}2}$ except the in-plane field direction is dramatically enhanced compared to bulks, following a definite relation distinct from bulk one between ${H}_{\mathrm{c}2}$ and the transition temperature. The anomalous enhancement of ${H}_{\mathrm{c}2}$ is highly suggestive of important changes of the superconducting properties, possibly accompanied with rotation of the triplet $d$ vector. Our findings will become a crucial step to further explore exotic properties by employing ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}$ thin films.