Invoke-Command -computername SERVERNAME { 
    Get-ChildItem -path E:\dfsroots\datastore2\public
} | Where-Object {{ 
        $_.extension-match "xls" -or $_.extension-match "xlk" 
    } -and { $_.creationtime -ge "06/01/2014"}
}

Above is my code example. I'm trying to remotely run this PowerShell code on my file server and have it return all .xls and .xlk files with a creation date on or later than 6/1/2014. When I run this code it starts spitting out all of the folders in that remote location. If I only compare two things like so:

Invoke-Command -computername SERVERNAME { 
    Get-ChildItem -path E:\dfsroots\datastore2\public
} | Where-Object { 
    $_.extension-match "xls" -and  $_.creationtime -ge "06/01/2014"
}

Only the .xls files created on or after that date display. What's going on here? Do I need to use something other than nest -and and -or statements?