How to get a file from the backend withou getting it JSON-parsed

I’m able to get an xlsx file from my rails backend with a GET-Request to “/companies/export_xslx”, now I’m facing the problem of getting the file passed the JSON parser. For every request the console shows “JSON.parse: unexpected character at line 1 column 1 of the JSON data”.

This is my setup:

//company model ...
exportXlsx: function() {
  const adapter = this.store.adapterFor('company');
  return adapter.exportXlsx();
}

//adapters/company.js
import DS from 'ember-data';
import TokenAuthorizerMixin from 'ember-simple-auth-token/mixins/token-authorizer';

export default DS.JSONAPIAdapter.extend(TokenAuthorizerMixin, {

  exportXlsx() {
    const url = 'companies/export_xlsx';
    return this.ajax(url, 'GET',
      { dataType: 'text',
         accepts: { xlsx: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet'
       } });
  }
});

I’ll try to alter the default accept header but the requests gets sent with “Accept: application/vnd.api+json”.

I already tried different approaches with “ember-custom-actions” or “ember-cli-file-saver”, they all failed with the JSON.parse… response.