Angular: How to download a file from HttpClient?

I need download an excel from my backend, its returned a file.

When I do the request I get the error:

TypeError: You provided 'undefined' where a stream was expected. You can provide an Observable, Promise, Array, or Iterable.
​

My code is:

this.http.get(`${environment.apiUrl}/...`)
.subscribe(response => this.downloadFile(response, "application/ms-excel"));


I tried get and map(...) but didn't work.

Details: angular 5.2

references:

import { HttpClient } from '@angular/common/http';
import 'rxjs/add/observable/throw';
import 'rxjs/add/operator/finally';
import 'rxjs/add/operator/map'
import 'rxjs/add/operator/catch';


Content-Type of response:

Content-Type: application/ms-excel


What's wrong?

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