Creating index on new field creation via REST in sharepoint 2013

Hello,

I use JSON to create fields in a sharepoint list:

{ '__metadata': { 'type': 'SP.Field' }, 'Title': champ, 'FieldTypeKind': type,'Required': requis, 'EnforceUniqueValues': false,'StaticName': champ});

If I set EnforceUniqueValues to true, I got an error meaning that the field should have an index.

I don't know how to create an index on the field via REST.

Any idea?

Thanks