Font Awesome 5 Pseudo

Problems with external link icon in

HTML

<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.0.6/css/all.css">
<a href="#" class="external">External</a>
<br>
External Link icon i tag: <i class="fas fa-external-link-alt"></i>
<br>
<a href="#" class="other">Other Icon</a>

CSS

a.external:after {
  font-family: 'Font Awesome 5 Free';
  content: '\f35d';
}

a.other:after {
  font-family: 'Font Awesome 5 Free';
  content: '\f152';
}