Downloading xml file from atom / rss feeds using CURL

[FreeBenzine]

Hi, I am trying to download xml file from URLs containing feeds using CURL using the following code. The code downloads the xml file for LINK1 (below, for RSS feeds). The code downloads a HTML file (instead of xml) for LINK2 (below, for Atom feeds). If I open LINK2 in a browser I can save it as a xml file. I do not understand why the code cannot download the xml file for LINK2. Any help will be highly appreciated.

//$url = 'https://rss.sciencedirect.com/publication/science/00221694'; //LINK1
$url = 'https://onlinelibrary.wiley.com/feed/25780727/most-recent'; //LINK2

$curl = curl_init($url);
curl_setopt($curl, CURLOPT_URL, $url);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl,CURLOPT_USERAGENT,'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.13) Gecko/20080311 Firefox/2.0.0.13');

curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, false);
curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);

$resp = curl_exec($curl);
curl_close($curl);

$myfile = fopen('x.xml', "w") or die("Unable to open file!");
fwrite($myfile, $resp);
fclose($myfile);

[FreeBenzine]

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