[Solved] mat-icon is not a known element in Angular

Hi,

I am trying to add the following:

<button mat-fab color="primary" aria-label="Example icon button with a delete icon">
   <mat-icon>delete</mat-icon>
</button>

I get this error:

Error: src/app/FamilyDocuments/familydocs/familydocs.component.html:9:9 - error NG8001: 'mat-icon' is not a known element:
1. If 'mat-icon' is an Angular component, then verify that it is part of this module.
2. If 'mat-icon' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message.    

I did install it:

npm i material-icons

it is not working.