Anisotropic inflation with derivative couplings

We thank Gianmassimo Tasinato for discussions. S. K. was supported by IKERBASQUE, the Basque Foundation for Science, and the Basque Government (IT-979-16), and Spanish Ministry MINECO (FPA2015-64041-C2-1P). I. Z. was partially supported by the STFC Grants No. ST/N001419/1 and No. ST/L000369/1. S. K. would like to thank the Physics Department at Swansea University for warm hospitality and the College Research Fund for financial support. J. H. was supported by a Swansea College of Science Doctoral Training Centre (DTC) Research Scholarship funded partly by Swansea University and partly by the STFC.