I have the following files:
Your issue is because the new Router doesn't accept [routerLink] on <button> elements, only <a> tags.
But you're in luck, Material lets you do the icon on <a> and <button>
Material Docs on md-button
So try this:
<a md-icon-button
[routerLink] = "['new-patient']"
color = "accent">
<md-icon class = "material-icons md-24">person_add</md-icon>
</a>