Physics Material - Character Slides Too Much

I am currently working on a 2D platformer. I am using a prefab from the AssetStore for my character (The last paragraph contains a link to the prefab). The character has a circle collider for his feet so that he can walk up slopes.

The problem I’m having is that because it is a circle collider, he also slides down any slope. I realize that I can add a Physics Material to the collider with a friction variable to stop (or at least resist) the sliding, but if I add any friction above ~0.1 the character can collide with a wall to stop himself from falling and yet 0.1 isn’t even enough to stop him from sliding down slopes.

So my question is, how can I stop the character from sliding down slopes in a way that doesn’t allow the player to stop himself from falling by colliding with walls?

The prefab that I’m using specifically is an asset found here, it’s disk location is Sample Assets/2D/Prefabs/2D Character

When the character is in the air, set the friction of the material to 0.

void Update()
    collider2D.sharedMaterial.friction = grounded ? groundFriction : 0f;

I’m not in Unity at the moment, so I can only refer to this. It seems like only the sharedMaterial is available to be modified. In that case, make sure your character uses it’s own physics material or you create one at runtime.