As we were talking about him, he suddenly materialised at the door.

materialised 是动词 materialise 的过去式，由名词 material（物质）加上动词后缀 -ise 构成，字面意思是"使物质化"，引申为"突然出现"或"显现"。这个词常用来描述某人或某物出人意料地出现。