convert xapi file to xml file

I'm making an http get request this way, in angular:

this.http.get('http://www.overpass-api.de/api/xapi?*[amenity=hospital][bbox=13.20524,43.70861,13.22842,43.72338]')
.subscribe(
data => {
    console.log(data.toString());
 });

but the following error is given:

Cannot read property 'toString' of null

I've also tried mapping the result this way:

this.http.get('http://www.overpass-api.de/api/xapi?*[amenity=hospital][bbox=13.20524,43.70861,13.22842,43.72338]')
.map(res => res.toString())
.subscribe(
data => {
    console.log(data);
 });

but the error remains. The xapi file I get if I go to http://www.overpass-api.de/api/xapi?*[amenity=hospital][bbox=13.20524,43.70861,13.22842,43.72338] is not null, so I'm supposing the method can't read the xapi file. Is there a way I can convert it to xml file?