Please note that the Materialize icons are shipped in a separate font file. This font file is automatically registered
by the [[\macgyer\yii2materializecss\assets\MaterializeAsset|MaterializeAsset]].
If you do not load the default [[\macgyer\yii2materializecss\assets\MaterializeAsset|MaterializeAsset]] make sure to at least load
[[\macgyer\yii2materializecss\assets\MaterializeFontAsset|MaterializeFontAsset]] (or another source providing the font file) to correctly
display the icons.