Nodeless superconductivity in the SnAs-based van der Waals-type superconductor NaSn2As2 E. J. Cheng, J. M. Ni, F. Q. Meng, T. P. Ying, B. L. Pan, Y. Y. Huang, Darren C. Peets, Q. H. Zhang and S. Y. Li EPL, 123 4 (2018) 47004 Published online: 18 September 2018 DOI: 10.1209/0295-5075/123/47004